Light micrograph of vitamin A, an essential nutrient necessary to the visual system, cell growth, epithelial tissue, embryogenesis, spermatogenesis, hematopoiesis, cell signaling, immune system, and reproduction. It also has a role as antioxidant, in gene expression, in bone and brain development, and in cancer stem cell differentiation. Dietary vitamin A is found as provitamins like 帣-carotene in fruits and vegetables such as carrots and spinach. Retinol, the animal form of vitamin A, exists in liver, meats, eggs, milk, and fish fat. Some manifestations of vitamin A deficiency are night blindness, hyperkeratosis, poor growth, and weakened immunity. Some therapeutic uses are: xerophthalmia, inhibiting carcinogenesis, vitamin A deficiency, and to improve immunity. Excessive intake of vitamin A can cause serious damage and even death. Field of view size: 1.49 x 2.23 mm (0.059 x 0.088 in)