Just like a wall is made up of many bricks, keratin - being a protein - is the result of the aggregation of simpler elements: amino acids (including cysteine, serine, glutamic acid, threonine, glycine and arginine). These are organized between them to form first long chains, then more complex structures, to form keratin filaments that unite in a "helix, similar to that of DNA, thanks to the disulfide bridges (ie bonds between the sulfur atoms) between the different molecules of cysteine, saline bonds, hydrogen bridges and the intervention of various other proteins. It is these strong chemical interactions that make the hair strong, compact and elastic, ensuring the right resistance to traction. The particular α-helix conformation of the keratin allows , on the other hand, to maintain a tight cohesion which confers rigidity, stability and resistance, but at the same time, by virtue of the hydrogen bridges present, it maintains a certain flexibility. the next level is represented by the "winding of three α-helices together: this" organization forms a protofibril. Eventually, the aggregation of numerous strands into bundles constitutes the cortex of the hair.
