Also called pigment, melanin is a substance that gives the skin and hair its natural color. It also gives color to the iris of the eye, feathers, and scales. In humans, those with darker skin have higher amounts of melanin. By contrast, those with less pigment have lighter or more fair skin coloring.
Melanin, sometimes referred to as a chemical, is formed as part of the process of metabolizing an amino acid called tyrosine. In the skin, melanin is formed by cells called melanocytes. Certain medical conditions, such as albinism, are associated with the lack of melanin. Albinism is a condition marked by the absence of a normal amount of pigment in the body. Animals, humans, and even plants can have albinism.
Albinism exists in a number of variations. Depending on the type of albinism, the skin, hair, and eyes may all be affected. In fact, ocular albinism affects not only the color of the eyes, hair, and skin, but also results in poor vision. Additionally, some types of melanin deficiency are associated with increased mortality rates.
Melanin provides many benefits to human beings. One of the most recognized benefits involves ultraviolet rays of the sun. Melanin provides a natural protection against the harmful effects of these rays. However, it does not provide complete protection from the sun, and individuals with darker skin tones are still at risk from the sun’s damaging rays.
Source: What is Melanin? (with pictures)