The Science Library

Editorial explainers on hair structure, bleach damage, click chemistry, tensile testing, and molecular reconstruction. Written to clarify the mechanism before the claim.

All articles

A glossy lock beside lab glass and a serum drop, molecular hair repair.What Is Molecular Hair Repair?

What Is Molecular Hair Repair?

Molecular hair repair explained with mechanism-first language and internal links to ANATOMY's science and complete protocol.

Read more about What Is Molecular Hair Repair?

A single hair fibre catching a precise point of light, click chemistry for haircare.Click Chemistry for Haircare, Explained

Click Chemistry for Haircare, Explained

A plain-English explanation of click chemistry in haircare and how ANATOMY connects the logic to molecular reconstruction.

Read more about Click Chemistry for Haircare, Explained

A hair fibre clamped and stretched for measurement, hair tensile testing.What Is Tensile Testing for Hair?

What Is Tensile Testing for Hair?

Tensile testing for hair explained: what is measured, why cross-sectional area matters, and how to interpret pre/post fiber data.

Read more about What Is Tensile Testing for Hair?

A hair fibre split to show cuticle and cortex, cuticle versus cortex damage.Cuticle vs Cortex Hair Damage

Cuticle vs Cortex Hair Damage

Cuticle vs cortex damage explained: what each layer does, why coatings are limited, and how ANATOMY connects the problem to molecular reconstruction.

Read more about Cuticle vs Cortex Hair Damage

Glossy platinum blonde waves, a bleached hair repair guide.Bleached Hair Repair: What Actually Works

Bleached Hair Repair: What Actually Works

A structural guide to bleached hair repair, gummy hair, oxidative damage, and ANATOMY's bundle-first reconstruction protocol.

Read more about Bleached Hair Repair: What Actually Works

A limp wet over-processed blonde lock, gummy bleached hair.Why Bleached Hair Feels Gummy

Why Bleached Hair Feels Gummy

Why bleached hair feels gummy, what it suggests structurally, what to avoid, and how ANATOMY explains the problem through reconstruction.

Read more about Why Bleached Hair Feels Gummy

A scorched hair tip near a warm glow, heat damaged hair structure.Heat Damaged Hair: How to Tell, What Lasts and How to Fix It

Heat Damaged Hair: How to Tell, What Lasts and How to Fix It

Hot tools change hair a little more with every session, and the hair cannot undo it. If yours feels best the day you straighten it and worst after the next wash, that pattern often points to heat damage. You can find where it sits, stop adding to it and trim it away as new hair grows in.

Read more about Heat Damaged Hair: How to Tell, What Lasts and How to Fix It

A hair fiber broken across its width, magnified under a microscopeWhy Is My Hair So Frizzy? How to Find the Cause and Get Rid of Frizz

Why Is My Hair So Frizzy? How to Find the Cause and Get Rid of Frizz

Frizz is neighboring hairs falling out of step, and only one of its causes is damage. Work out which one you have before you change anything.

Read more about Why Is My Hair So Frizzy? How to Find the Cause and Get Rid of Frizz

Two hair fibers under a light microscope; a paler fiber ends in a break across its widthDoes Coloring Damage Hair? What Dye and Perms Do to Each Strand

Does Coloring Damage Hair? What Dye and Perms Do to Each Strand

Permanent color, perms and relaxers all change the keratin in the hair they touch, and on longer hair the treated lengths can stay on your head for years. Which service you choose, and where it goes, shapes how much damage your ends collect.

Read more about Does Coloring Damage Hair? What Dye and Perms Do to Each Strand

Two hair fibers under a light microscope, the paler one broken across its widthProtein Treatment for Hair: What It Does and When You Need One

Protein Treatment for Hair: What It Does and When You Need One

Hair is mostly protein, yet the protein in a mask never becomes part of its keratin. What a treatment does instead, how long it stays, and how to tell whether your lengths need one.

Read more about Protein Treatment for Hair: What It Does and When You Need One

Bleached hair under a light microscope, thin flakes lifting along one edge of the fiberWhat Does Leave-In Conditioner Do, and How Do You Use It?

What Does Leave-In Conditioner Do, and How Do You Use It?

Its main job is lowering friction, so the hair that gains most is hair that tangles: long, lightened, heat-styled or curly lengths. Short, untreated hair that already combs freely may not need one at all.

Read more about What Does Leave-In Conditioner Do, and How Do You Use It?

Hair fiber under a light microscope, both edges in view, with scale edges standing away from the surface along one sideHow to Repair Damaged Hair: What Can Be Fixed and What Cannot

How to Repair Damaged Hair: What Can Be Fixed and What Cannot

Two scientific reviews seem to disagree about whether damaged hair can be repaired, and both are right. The difference decides what a product can change until the next wash, and what only scissors and new growth can.

Read more about How to Repair Damaged Hair: What Can Be Fixed and What Cannot

Two hair fibres under a light microscope; the paler fibre ends in a breakHair Breakage: What Causes It and How to Stop It

Hair Breakage: What Causes It and How to Stop It

Hair breakage rarely comes from a straight pull; a strand snaps where it bends sharply over another hair in a tangle. Bleach, heat and sun make that break easier, and the hairs in your brush hold clues to which one is at work.

Read more about Hair Breakage: What Causes It and How to Stop It

Split Ends: What They Are, What Causes Them, and How to Stop Them

The tips of shoulder-length hair are about two years old, and a split end is that old hair coming apart along its length. Some products can hold it together until the next wash; only scissors remove it.

Read more about Split Ends: What They Are, What Causes Them, and How to Stop Them

A hair lock submerged in cloudy hard water with mineral bubbles, hard water and hair.Hard Water and Hair: Why Minerals Stiffen Your Strands

Hard Water and Hair: Why Minerals Stiffen Your Strands

Hard-water minerals like calcium, copper, and iron build up in hair, stiffen it, and dull color, especially in porous hair. Chelating shampoos clear them.

Read more about Hard Water and Hair: Why Minerals Stiffen Your Strands

A glossy twisted rope of hair like a protein cable, keratin.Keratin: The Protein Your Hair Is Made Of

Keratin: The Protein Your Hair Is Made Of

Keratin is the structural protein that makes up hair. Understanding it explains what keratin treatments can and cannot do.

Read more about Keratin: The Protein Your Hair Is Made Of

A waterlogged limp swollen lock, hygral fatigue.Hygral Fatigue: Why Damaged Hair Gets Worse Every Wash

Hygral Fatigue: Why Damaged Hair Gets Worse Every Wash

Hygral fatigue is the slow wear from hair swelling when wet and shrinking when dry. Damaged hair cannot repair itself, so each wet-dry cycle adds to the damage.

Read more about Hygral Fatigue: Why Damaged Hair Gets Worse Every Wash

A single hair fibre with internal crosslinks glinting within, disulfide bonds.Disulfide Bonds: The Cross-Links That Make Hair Strong

Disulfide Bonds: The Cross-Links That Make Hair Strong

Disulfide bonds are the sulfur cross-links that hold the hair cortex together. Bleach breaks them; rebuilding them is what restores strength.

Read more about Disulfide Bonds: The Cross-Links That Make Hair Strong

A frayed fibre revealing inner fibrils, the hair cortex.The Hair Cortex: Where Your Hair's Strength Lives

The Hair Cortex: Where Your Hair's Strength Lives

The cortex is the strand's core, a cable of twisted protein held by disulfide bonds. It decides how strong your hair is and what snaps when it breaks.

Read more about The Hair Cortex: Where Your Hair's Strength Lives

Macro of overlapping cuticle scales on a hair fibre, the hair cuticle.The Hair Cuticle: The Scale Layer That Protects the Strand

The Hair Cuticle: The Scale Layer That Protects the Strand

The cuticle is the layer of overlapping scales, like roof tiles, that armors the hair strand. When it lifts, hair turns rough, dull, and porous.

Read more about The Hair Cuticle: The Scale Layer That Protects the Strand

Three hair locks compared on marble, three bond-repair mechanisms.ANATOMY vs Olaplex vs K18: How They Differ

ANATOMY vs Olaplex vs K18: How They Differ

Three bond-repair systems, three different chemistries. Click-chemistry covalent crosslinking, single-bond bis-aminoethanethiosulfonate, and oligopeptide repair — compared on mechanism, peer-reviewed data, and outcomes. By ANATOMY.

Read more about ANATOMY vs Olaplex vs K18: How They Differ

Water soaking into a bleached blonde lock, bleached hair and high porosity.Is Bleached Hair Always High Porosity?

Is Bleached Hair Always High Porosity?

Yes — almost always. The science of how bleach changes the hair cuticle and cortex, the timeline, and what restores porosity. Peer-reviewed answer. By ANATOMY.

Read more about Is Bleached Hair Always High Porosity?

Water soaked into a dull saturated damaged lock, high porosity hair.High Porosity Hair: What It Is and What Fixes It

High Porosity Hair: What It Is and What Fixes It

High porosity hair is usually damaged hair: a stripped surface and a weakened cortex. The causes, the evidence and what helps. The peer-reviewed causes, the Class 1/2/3 repair taxonomy, and what actually works. By ANATOMY.

Read more about High Porosity Hair: What It Is and What Fixes It

Water beading and rolling off glossy sealed hair, low porosity hair.Low Porosity Hair: The Real Science

Low Porosity Hair: The Real Science

Low porosity hair is structurally low-porosity virgin or near-virgin hair. What actually penetrates it (and what does not), how to test it, and the truth about "low porosity hair products." By ANATOMY.

Read more about Low Porosity Hair: The Real Science

A product droplet wrapping a single frayed fibre, do bond builders work.Bond Repair Treatment: Does It Work, and Which Kind Do You Need?

Bond Repair Treatment: Does It Work, and Which Kind Do You Need?

Two words on a label can stand for several unrelated chemistries, and little of the evidence behind them is independent. If your hair has never been lightened, colored, relaxed or permed, you probably do not need one.

Read more about Bond Repair Treatment: Does It Work, and Which Kind Do You Need?

A dry lock with a lather bubble and droplet, best shampoo for dry hair.How to Choose the Best Shampoo for Extremely Dry Hair

How to Choose the Best Shampoo for Extremely Dry Hair

Library Dry hair is not always a moisture problem. A mechanism-first guide to choosing shampoo when hair feels dry, brittle, porous, or structurally weakened. Published February 28, 2026 Updated April 26, 2026 Science Library Contents AnswerDryness vs damageShampoo roleAvoidSelection frameRoutineStructureProtocolReferences...

Read more about How to Choose the Best Shampoo for Extremely Dry Hair