Iron is an example of a micronutrient. A micronutrient is defined as a nutrient that is only needed in very small amounts. Humans need micronutrients to manufacture hormones, produce enzymes and carry out other functions.
Vitamins and minerals are classified as micronutrients because the human body only needs small amounts of them to survive. Vitamins A, D, E and K are classified as fat-soluble vitamins because they are stored in the body's fatty tissues. B vitamins and vitamin C are classified as water-soluble vitamins. Any excess of these vitamins is excreted in urine. Humans also need minerals such as chromium, fluoride, copper, cobalt and zinc in small amounts to survive.