The hair, we usually mean the fur on our heads. The color of hair is controlled by genes; Generally speaking, it is common to see black, golden yellow, brown, and red hair. It will become white when the human aging.Only human hair will grow long all the time, so the human need a haircut when the hair become long, But it doesn’t happen to the animals. The reason for this is not clear,
The human head can contain up to several hundred thousand hairs, with a maximum of about 500,000. The length of hair is the longest all the fur, especially in women, some can grow to 90 ~ 100 cm, even up to 200 cm. normal condition, the hair grew longer about 0.3 mm every day. But the sun can make hair grow quickly. Generally, the life of hair is about 2 to 4 years, some even up to 6 years. Hair will be up to exceeding 6 m in length if it isn’t cut short.
By the difference of race and region, the color of hair is diverse, including black, golden yellow, red, brown, red, brown, yellow, gray, and even a green and red. It can also Change a variety of colors through dye. Scientific studies have shown that: The color of hair is decided by its metal elements; black color hair contains the same amount of copper, iron and melanin. It will become white when increasing the content of nickel, there is titanium in the Golden hair, and there is molybdenum in reddish brown hair. In some African countries, some child's color of hair is red, which is caused by a severe lack protein.