Polarised light micrograph of crystals of vitamin C (ascorbic acid). Vitamin C has a monoclinic crystal structure, characterised by three unequal axes, one pair of which are not at right angles. Most fruit and vegetables are high in vitamin C content. The average man or woman requires 70 milligrams per day; children and pregnant woman need an additional amount. A deficiency in vitamin C causes scurvy. The biochemical function of vitamin C is as a regulator in tissue respiration. Magnification: x80 at 6x4.5 cm size.