Polarised light micrograph of recrystallized glycine, the simplest of the amino acids. Glycine is a neurotransmitter. It is important in metabolism as it contributes carbon atoms in the formation of the blood pigments. Glycine is also used in the synthesis of adenine and guanine, two of the nucleotides used to form nucleic acids (DNA and RNA). Magnification: x93 when printed at 10 cm wide.