Fingernails, bones and teeth are the three hardest tissues in the human body, partly because they contain little water, only about ten percent. However, nails are capable of absorbing water, and if they are immersed in water, the water content of the nails increases dramatically, causing them to soften. Nail growth principle and structure Nails are composed of keratin, which is a dead cell, and it will continue to grow because it is constantly extruded by the living cells of the nail bed. The nail is the protective layer of the finger, which protects the fingertip, which is rich in nerves, from injury. Nails are made of egg nails, which are made of keratin, a dead cell that grows because it is constantly being pushed out by the living cells of the nail bed. Nails are like a microcosm of the body and can reflect the state of health. Normal human nails are usually smooth, pinkish, and translucent and curved. The nail is a hard tissue, divided into the nail edge, that is, the most anterior part of the nail; the nail edge, that is, the nail and the internal adhesion of the edge part; the first 1/3 of the nail for the nail before, in the middle 1/3 of the nail in the middle, the second 1/3 of the nail for the root of the nail. The sides of the nail are the lateral nail. All parts of the finger, except the nail portion, are collectively referred to as soft tissue. The front end of the skin edge, the back end of the nail root and the back of the finger skin connected to a thin and neat, like a belt, called the belt, the belt connected to the normal skin tissue and joints above the belt is called the skin capsule. Nails in 97% of the composition is protein, so should be appropriate for the baby to eat some fish, shrimp and other high-protein food. In addition walnuts, peanuts can make the nails strong, other trace elements of zinc, potassium, iron supplementation is also very important. The chemical composition of nails is similar to that of hair, mainly composed of sulfur-rich protein keratin. Nail formation, at first soft jelly-like cells, cell death hardened, tightly stacked up exposed and become nails. The skin that covers the top of the nail root is called the nail epidermis, and its function is to prevent soil, irritants and microorganisms from invading the sensitive cells at the root of the nail. The skin underneath the nail has a large amount of blood flow through it, and there are many microvessels near the surface of the skin that give the nail a pinkish color. It is composed of white matter, keratin and sulfur, and it grows 0.05-1.2 millimeters a week, which is about four times faster than the growth rate of the toenail. The longer the finger, the faster the nail grows. Heat causes nails to grow faster. Nails grow faster in summer than in winter, faster in the south than in the north, and faster during the day than at night. Right-handed people grow their nails faster; left-handed people grow their nails faster. The record for the longest fingernails was set by an Indian man who had fingernails on one hand for more than 35 years and had fingernails up to 81 centimeters long. A person must be well nourished for the nails to grow properly. If a person is malnourished or suffers from anorexia nervosa, the nails will grow slowly and develop horizontal grooves called Beau’s lines. Malnutrition can also lead to nails become brittle and easy to break usually nails accounted for the fingers not save 3 / 5, was rectangular arch, the top of the transverse diameter is slightly larger than the base of the transverse diameter of the base of the nail white like a half-moon shaped part of the nail called nail half-moon, that is, the folk commonly known as the nail white, located in the center of the finger symmetry, no major deviation. That said, when all the fingernails have the right amount of nail white, it can be deduced that the human body is in good health. If 10 fingernails have no or only a little white, it means that the body is tired or is suffering from a disease. The ideal nail white should account for about 1 / 5 of the nail area, nail white is too big or all do not mean that the body is very strong. Therefore, everyone should take care of our nails as much as we take care of our skin.