National Geographic Learning
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Unit 7

Leather
from a Lab

The future of materials — grown, not killed
Lead-in 01

Could science make leather without harming any animals?

Leather is everywhere — your shoes, your bag, your jacket. But the industry behind it harms billions of animals every year. Now scientists are asking: what if we could grow leather in a lab instead?

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The Hidden Cost

A billion animals killed for leather every year

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Biofabrication

Growing materials from cells in a lab

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Step by Step

How scientists turn cells into leather sheets

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Beyond Leather

Could we grow meat the same way?

Let's explore how biofabrication could transform the way we make things — forever.

Skimming 02

Quick Overview

Skim the article in 90 seconds, then check your answers.

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The Problem

What harm does the global leather industry cause?

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The Process

What are the main steps for growing leather in a lab?

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Forgacs's Vision

What does Andras Forgacs believe about biofabrication's future?

The Problem: The global leather industry kills over a billion animals every year.

The Process: Scientists take cells from an animal → isolate and grow them in a lab → expand millions into billions → spread into thin sheets → layer into thick sheets → tan, dye, and finish.

Forgacs's Vision: He calls biofabrication a "natural evolution of manufacturing for mankind" — a more efficient, responsible, and creative way to make products, possibly including lab-grown meat.
Paragraph 1

Popularity at a Price

Leather is everywhere — but its hidden cost raises a crucial question.

Reading 03

Opening List

Leather is a hugely popular material for a range of products: shoes, jackets, bags, wallets—the list goes on. But this popularity comes at a price. The global leather industry kills over a billion animals every year. This has caused many to ask the question: Is it possible to meet the global demand of leather but not do any harm to animals? A process called biofabrication may be the answer.
The colon signals that a list of examples is coming. The list itself — shoes, jackets, bags, wallets — is a rapid asyndeton (no conjunctions), creating a sense of accumulation. But crucially, "the list goes on" refuses to close the list. This open-ended structure implies that leather products are too numerous to name — reinforcing the claim "hugely popular" before it is stated. It invites readers to mentally add their own examples, making the argument feel personally relevant.
Reading 04

Pivot Sentence

Leather is a hugely popular material for a range of products: shoes, jackets, bags, wallets—the list goes on. But this popularity comes at a price. The global leather industry kills over a billion animals every year. This has caused many to ask the question: Is it possible to meet the global demand of leather but not do any harm to animals? A process called biofabrication may be the answer.
The short, punchy sentence creates a dramatic pause after the long opening. In prose rhythm, a sudden short sentence after a long one acts like a full stop — it forces the reader to slow down and absorb the pivot. "But" immediately signals reversal. "Comes at a price" is a familiar idiom that readers understand instantly, which makes the abstract cost feel intuitive before it is named. The brevity mimics the abruptness of an uncomfortable truth — there's no softening.
Reading 05

Shocking Statistic

Leather is a hugely popular material for a range of products: shoes, jackets, bags, wallets—the list goes on. But this popularity comes at a price. The global leather industry kills over a billion animals every year. This has caused many to ask the question: Is it possible to meet the global demand of leather but not do any harm to animals? A process called biofabrication may be the answer.
The two scale markers are "global" (geographic scale — this is worldwide, not local) and "over a billion" (numerical scale — an almost incomprehensible number). Together they create a double maximization: no part of the world is exempt, and the quantity is vast. The word "kills" is also notable — not "uses" or "involves" but the blunt verb "kills." This direct word choice is a deliberate rhetorical choice to make the moral weight of the statistic clear.
Reading 06

Embedded Question

Leather is a hugely popular material for a range of products: shoes, jackets, bags, wallets—the list goes on. But this popularity comes at a price. The global leather industry kills over a billion animals every year. This has caused many to ask the question: Is it possible to meet the global demand of leather but not do any harm to animals? A process called biofabrication may be the answer.
Attributing the question to "many" signals that this is a widely shared concern, not just one person's viewpoint. It transforms the question from individual opinion to collective inquiry, lending it moral legitimacy. The structure "caused many to ask" also establishes causation: the statistic (S3) directly produces the question (S4), making the logical chain explicit. The embedded colon + question mirrors the colon + list in S1, creating a structural echo that ties the paragraph together.
Reading 07

Tentative Answer

Leather is a hugely popular material for a range of products: shoes, jackets, bags, wallets—the list goes on. But this popularity comes at a price. The global leather industry kills over a billion animals every year. This has caused many to ask the question: Is it possible to meet the global demand of leather but not do any harm to animals? A process called biofabrication may be the answer.
"May be" is a hedging modal — it signals possibility, not certainty. Using "is" would be an overstatement, as the technology is still emerging. This honest tentativeness builds credibility and scientific accuracy. Structurally, this sentence is the thesis statement of the article — it introduces "biofabrication" by name for the first time and promises to answer the question posed in S4. The entire article is essentially an expansion of this single claim.
Paragraph 2

What Is Biofabrication?

From growing human ears to custom leather — biofabrication is already changing what's possible.

Reading 08

Not New

Biofabrication is not new; it is already commonly used in medicine. Biofabrication techniques are used to grow body parts like ears, skin, and bones for transplants. But it can also be used to make other products, such as leather. Biofabricated leather has many advantages. Scientists will be able to make it with whatever qualities they want, such as extra softness, greater strength, or even different colors and patterns.
The semicolon links two closely related independent clauses — the second immediately explains the first. Leading with "not new" is a rhetorical strategy to preempt skepticism: a reader might assume biofabricated leather is experimental or unreliable. By stating it's already established — and in medicine, no less — the writer immediately builds credibility and trust. "Already commonly used" reinforces that this is mature, proven technology, not a speculative idea.
Reading 09

Medical Applications

Biofabrication is not new; it is already commonly used in medicine. Biofabrication techniques are used to grow body parts like ears, skin, and bones for transplants. But it can also be used to make other products, such as leather. Biofabricated leather has many advantages. Scientists will be able to make it with whatever qualities they want, such as extra softness, greater strength, or even different colors and patterns.
The list moves from external/delicate (ears) to internal/structural (bones), implying a progression from surface to depth. This is a subtle form of climactic ordering — saving the most structurally significant item for last. Ears are visible and complex in shape; skin is a large organ; bones are the structural foundation of the body. The variety also demonstrates versatility: biofabrication can handle different tissue types, shapes, and functions. This broad capability makes the transition to leather seem plausible.
Reading 10

Extension to Leather

Biofabrication is not new; it is already commonly used in medicine. Biofabrication techniques are used to grow body parts like ears, skin, and bones for transplants. But it can also be used to make other products, such as leather. Biofabricated leather has many advantages. Scientists will be able to make it with whatever qualities they want, such as extra softness, greater strength, or even different colors and patterns.
"But" signals a pivot from the established use (medicine) to a new possibility (leather). "Also" signals this is an addition, not a replacement — medicine remains the primary context. Together, "but… also" creates a contrast-plus-expansion structure: "Yes, [established thing] — but also [new thing]." The modal "can" (rather than "is") signals this is a possibility or capability, not yet a widespread practice — consistent with the article's careful hedging of emerging technology.
Reading 11

Advantages Claim

Biofabrication is not new; it is already commonly used in medicine. Biofabrication techniques are used to grow body parts like ears, skin, and bones for transplants. But it can also be used to make other products, such as leather. Biofabricated leather has many advantages. Scientists will be able to make it with whatever qualities they want, such as extra softness, greater strength, or even different colors and patterns.
The sentence functions as a topic-narrowing transition — after introducing biofabrication broadly (S1–S3), it announces the specific focus of S5. "Many advantages" is an umbrella claim: deliberately vague, it creates a forward pull — the reader expects the advantages to be listed next. This structure (broad claim → specific detail) is a classic general-to-specific organization. The short, declarative style also contrasts with the longer technical sentences around it, giving the reader a moment to reset before the details.
Reading 12

Customizable Future

Biofabrication is not new; it is already commonly used in medicine. Biofabrication techniques are used to grow body parts like ears, skin, and bones for transplants. But it can also be used to make other products, such as leather. Biofabricated leather has many advantages. Scientists will be able to make it with whatever qualities they want, such as extra softness, greater strength, or even different colors and patterns.
"Whatever qualities they want" is a free relative clause emphasizing unlimited customization — scientists are not constrained by what an animal's hide naturally produces. Traditional leather is limited by the animal: its size, age, species, and natural skin quality. Lab leather flips this: design precedes material. The list — "extra softness, greater strength, or even different colors and patterns" — moves from functional properties to aesthetic ones, with the scalar "even" signaling that customization of appearance is a surprising bonus beyond what was already impressive.
Paragraph 3

The Process: Step by Step

From a single cell to a finished leather product — here's exactly how it's done.

Reading 13

Process Question

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
The rhetorical question "But how exactly does biofabrication work?" is a signposting device — it explicitly tells the reader that a shift is happening: from what biofabrication is to how it works. The word "exactly" signals precision and detail ahead, preparing the reader for a step-by-step explanation. "But" at the start also carries an implicit concession: "We've established what it can do — now let's explain the mechanism." This mirrors a classic expository structure: claim → evidence → explanation.
Reading 14

Cruelty-Free Start

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
The participial phrase "not hurting the animal in any way" is a negative participial modifier — it clarifies what does not happen during the process. Its placement after the main clause is strategic: it immediately addresses the reader's most likely concern (surely taking cells from an animal hurts it?). The phrase reassures the reader before they can object. The emphatic "in any way" leaves no room for partial doubt, reinforcing the cruelty-free promise that is the article's entire argument.
Reading 15

Isolation and Growth

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
"Then" is a temporal sequence connector — it signals that this step follows the previous one in time. In process descriptions, sequence connectors (begin, then, next, after that) create procedural clarity: the reader can follow the steps in order without confusion. "Then" here links step 1 (taking cells) to step 2 (isolating and growing them), maintaining the chronological flow. Notice how the paragraph builds a chain: begin → then → [scale expansion] → next → then → after that — each step logically dependent on the last.
Reading 16

Exponential Scale

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
"Takes" implies input — acquiring what already exists (millions of cells). "Expands" implies active multiplication — increasing what was taken exponentially. The contrast of "millions" and "billions" creates a dramatic leap that shows the productive power of the lab process. What's remarkable is the implied efficiency: starting from a tiny input (just a few cells from one animal) and producing a massive output (billions of cells). This scale is what makes the technology commercially viable — a single cell donation can supply a factory.
Reading 17

Forming Thin Sheets

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
The sequence connectors — begin, then, next, after that, then — form a procedural chain that mirrors how scientists actually write laboratory protocols. Each connector signals a discrete, ordered step where the previous step must be completed first. This structure is not just organizational; it reflects the dependency logic of the process: cells must be grown before they can be spread; thin sheets must exist before they can be layered. The connectors allow a complex, multi-stage scientific process to be communicated accessibly without losing accuracy.
Reading 18

Building Thickness

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
This technique is called lexical chaining with modification: the noun phrase "thin sheets" from S5 is repeated in S6, maintaining referential continuity (the reader knows exactly what "these thin sheets" refers to). The modification — adding "thicker" — shows progression: the same material evolves through the process. This mirrors the larger structural logic of the paragraph, where each sentence builds on the previous one. The technique is efficient: no new noun is introduced, reducing cognitive load while still advancing the process.
Reading 19

Open Finishing

But how exactly does biofabrication work? To grow leather, scientists begin by taking some cells from an animal, not hurting the animal in any way. They then isolate the cells and grow them in a lab. This process takes millions of cells and expands them into billions. Next, the scientists take the cells and spread them out to form thin sheets. These thin sheets are then layered to combine into thicker sheets. After that, the scientists can tan the hide. Anyone can then dye and finish the leather and design it in any way they like—into bags, watches, or shoes.
The shift from "the scientists" to "anyone" is a deliberate subject broadening. The early steps require specialized scientific knowledge (isolating cells, growing them in a lab). But dyeing, finishing, and designing leather are traditional craft skills — accessible to leather workers, designers, and artisans worldwide. The word "anyone" democratizes the final stage, suggesting that biofabricated leather integrates into existing industries without requiring all workers to be scientists. The em-dash list at the end — "bags, watches, or shoes" — echoes the opening list of S1, creating a satisfying structural callback.
Paragraph 4

A Natural Evolution

From leather to meat — one visionary sees biofabrication as the future of everything we make.

Reading 20

Advocate Introduction

Andras Forgacs supports biofabrication. He says it may even be a "natural evolution of manufacturing for mankind." We will be able to make the products we need in a more efficient, responsible, and creative way. And biofabrication is not just about leather—it's possible the technique could also be used to grow meat. While this may sound crazy, Forgacs certainly doesn't think so. "What's crazy," he says, "is what we do today."
The one-sentence introduction is deliberately unadorned — no title, no credential, just name + position. This creates a clean slate before his views are presented. It mimics journalistic neutrality: reporting who this person is without immediately coloring the reader's judgment. The brevity also mirrors the style of S2 in Para 2 ("Biofabricated leather has many advantages") — another short sentence before detailed elaboration. The simplicity signals that Forgacs's credibility will come from his words, not his introduction.
Reading 21

Bold Claim: "Natural Evolution"

Andras Forgacs supports biofabrication. He says it may even be a "natural evolution of manufacturing for mankind." We will be able to make the products we need in a more efficient, responsible, and creative way. And biofabrication is not just about leather—it's possible the technique could also be used to grow meat. While this may sound crazy, Forgacs certainly doesn't think so. "What's crazy," he says, "is what we do today."
"Natural evolution" is a powerful biological metaphor. "Evolution" implies an inevitable, gradual, and improvement-oriented process — not a radical disruption but a logical next step. "Natural" neutralizes fear of the technology by framing it as organic progression, not artificial interference. Together, they counter the objection that biofabrication is unnatural or dangerous by reframing it as part of how humanity naturally develops. Placing it in quotation marks signals it is Forgacs's own phrase — a deliberate, considered word choice, not casual language.
Reading 22

Triple Parallel Vision

Andras Forgacs supports biofabrication. He says it may even be a "natural evolution of manufacturing for mankind." We will be able to make the products we need in a more efficient, responsible, and creative way. And biofabrication is not just about leather—it's possible the technique could also be used to grow meat. While this may sound crazy, Forgacs certainly doesn't think so. "What's crazy," he says, "is what we do today."
The three adjectives form a tricolon, moving from practical → ethical → imaginative:
• "Efficient" — pragmatic appeal: better use of resources, less waste
• "Responsible" — moral/ethical appeal: accountability to animals and environment
• "Creative" — aspirational appeal: opening new design possibilities
The ordering is persuasive: it starts with what businesses care about (efficiency), moves to what ethicists care about (responsibility), and ends on what makes the technology exciting (creativity). This three-way appeal attempts to satisfy all potential audiences simultaneously.
Reading 23

Beyond Leather

Andras Forgacs supports biofabrication. He says it may even be a "natural evolution of manufacturing for mankind." We will be able to make the products we need in a more efficient, responsible, and creative way. And biofabrication is not just about leather—it's possible the technique could also be used to grow meat. While this may sound crazy, Forgacs certainly doesn't think so. "What's crazy," he says, "is what we do today."
"It's possible" and "could" are two layers of epistemic hedging — expressing that the claim is speculative, not established. This double hedging serves two purposes: (1) it maintains scientific accuracy — lab-grown meat is still experimental; (2) it softens a claim that the writer knows may shock readers, making it easier to accept. The em-dash before this clause creates a dramatic pause, giving the idea extra weight. The word "also" signals this is an extension of what's already been argued, not a separate, unrelated claim.
Reading 24

The Closing Reversal

Andras Forgacs supports biofabrication. He says it may even be a "natural evolution of manufacturing for mankind." We will be able to make the products we need in a more efficient, responsible, and creative way. And biofabrication is not just about leather—it's possible the technique could also be used to grow meat. While this may sound crazy, Forgacs certainly doesn't think so. "What's crazy," he says, "is what we do today."
The closing uses a classic rhetorical reversal: the article anticipated the reader's objection ("this may sound crazy"), then quotes Forgacs flipping the term entirely. "What's crazy… is what we do today" transfers the label from the solution to the current practice. The inversion ("What's crazy is…" rather than "What we do today is crazy") gives it an aphoristic quality — memorable and quotable. The split quotation — intercut with "he says" — also creates a rhythmic pause that makes the final claim land with greater force.
Language 25

Sequence Connectors in Process Writing

Organizing steps in logical, temporal order

begin by then next after that finally
A) Scientists begin by taking cells. They then isolate them. Next, cells form thin sheets. After that, sheets are layered.
B) begin by + -ing → then + verb → next, + verb → after that, + verb
C) ❌ Scientists take cells. They isolate them. The cells form sheets. The sheets are layered.  [no connectors = unclear sequence]
D) RULE: Process descriptions use sequence connectors to show that each step must come before the next. Always match connector to position in the sequence.
When describing a process, sequence connectors do two things: they signal time order (this happened before that) and they signal logical dependency (this couldn't happen without that). "Begin by + -ing" always signals the first step. "Then" and "next" are interchangeable for middle steps. "After that" suggests a step that requires completion of something more substantial first. "Finally" closes the sequence. Without connectors, a list of actions has no clear order — with them, it becomes a reliable procedure anyone can follow.
Language 26

Modal Verbs for Future Possibility

Expressing certainty, probability, and speculation

may will could can hedging
A) Biofabrication may be the answer.           [uncertain possibility — 50/50]
B) Scientists will be able to make leather with any qualities they want.  [confident future claim]
C) The technique could also be used to grow meat.    [speculative, theoretical]
D) RULE: will = confident prediction; may = uncertain possibility; could = theoretical / conditional possibility.
Modal verbs express how certain a speaker is about a future event. In science writing, choosing the right modal is crucial: "will" claims high confidence — use it when evidence strongly supports the prediction. "May" claims moderate confidence — use it when the outcome is plausible but not yet proven. "Could" is the most tentative — it suggests theoretical possibility, often in contexts where the evidence is preliminary. In this article, each modal is carefully chosen: "will be able to" for established lab capabilities; "may be" for the technology's potential; "could be used" for the more speculative idea of growing meat.
Language 27

Concession + Reversal: "While… / But…"

Acknowledging an objection before overturning it

while clause concessive reversal certainly rhetorical contrast
A) While this may sound crazy, Forgacs certainly doesn't think so.
B) But this popularity comes at a price. / But how exactly does it work?
C) ❌ This sounds crazy. Forgacs doesn't think so.  [two blunt statements — no acknowledgment of tension]
D) RULE: While + [concession], [counter-claim] = acknowledge the opposing view, then redirect. Stronger than simply stating your claim.
A "while" concession clause is a sophisticated rhetorical tool: it admits the opposing view is understandable before dismissing it. "While this may sound crazy" preempts the reader's skepticism — the writer says "I know what you're thinking" before overturning it. This is more persuasive than ignoring the objection, because it shows the writer has considered both sides. The adverb "certainly" in the response clause adds confident force to the counter-claim. Compare: "This sounds crazy but Forgacs disagrees" (flat) vs. "While this may sound crazy, Forgacs certainly doesn't think so" (controlled, confident, rhetorically aware).
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Lesson Complete
Unit 7 · Leather from a Lab

The Problem

Over a billion animals killed annually for leather — biofabrication offers a cruelty-free alternative.

Already Proven

Biofabrication is used in medicine to grow ears, skin, and bones — leather is the next step.

The Process

Cells → lab growth → millions to billions → thin sheets → thick sheets → tan, dye, finish.

Beyond Leather

Efficient, responsible, creative — biofabrication could transform how we make everything, including meat.

What's crazy is what we do today.