The hair of humans, rodents, and other mammals is a filament that grows from a follicle in the skin. It consists mainly of tightly packed, keratin-filled cells that vary in length and diameter. The different colors of human hair are the result of differences in the amount, distribution, and type of melanin pigment and surface structure. Other factors that influence the color of hair include its thickness, and how the light reflects from it.

Hair consists of two major parts: the shaft that protrudes from the skin, and the root, which is sunk below the epidermis in a pit (follicle). All follicles contain hair-producing cells; when these cells mature, they are shed out and replaced by new hair cells. The growth of hair is regulated by the hormones estrogen and testosterone. When the follicles are triggered to grow by these hormones, they produce an enzyme called tyrosinase that converts tyrosine into melanin. The color of human hair varies according to the amount of melanin produced by the tyrosinase enzyme.

There are five main colors of human hair: black, brown, blond, gray, and white/gray. The most common shade is black, which is produced by high levels of tyrosinase in the body. Other shades of human hair are created by changing the concentration or amount of melanin in the hair follicles, or by mutations of the gene that regulates the production of tyrosinase.

Hair has many functions, but its most important role is in heat insulation. Hair protects the body from extreme temperatures, and can also help cool the body by facilitating the evaporation of sweat. It also provides protection from ultra-violet radiation exposure. The function of hair in other locations on the body is less well understood. One theory is that it helps to keep the body warm by insulating the chest and abdomen, while another is that it impedes infection.

Aside from protecting the scalp, hair has a number of other specialized uses. For example, some subhuman primates have highly specialized hair follicles on the muzzle and lips that produce vibrissae, or whiskers. These whiskers are sensitive to pressure, and transmit nerve impulses to the brain about touch.

Hair can be colored using semi-permanent or permanent dyes, which deposit color in the hair shafts. Bleaching, on the other hand, strips all of the natural melanin from the hair, leaving it white or gray. Hair color can also be changed by using wigs, which are fabricated from real or synthetic human hair. Wigs can be worn in a variety of styles and can come in a wide range of textures and colors. When choosing a wig, experts recommend going to a store and trying on a few different styles to find the best fit. It is important to choose a style that matches your complexion and eyes, so you can feel confident when wearing it. You should also look for a wig that is easy to wear and will not require extra adhesives.