In a living being, proteins make up roughly everything: from the molecular machines running every cell's metabolism, to the tip of your hair. Encoded in the DNA, a protein may be represented as a thread of hundreds of individual molecules called amino acids, linked together. Depending on its particular amino acid combination, a protein folds in one way or another, resulting in a functional 3D shape. The shape makes the function, and with 20 different amino acids available, the possible combinations are countless.