Biotin crystals. Polarized light micrograph of crystals of the B-vitamin biotin, also known as vitamin B7, vitamin H and coenzyme R. This vitamin is required for cell growth, the production of fatty acids, and the metabolism of fats and amino acids. It is also used in the biotechnology industry to conjugate proteins for biotinylation. Biotin deficiency, a rare nutritional disorder, can become fatal if untreated. Biotin supplements are recommended during pregnancy and for strengthening hair and nails. It is found in many cosmetic and health products for the hair and skin. This is the D-biotin stereoisomer. Field of view size: 0.740 x 1.110 millimetres.