The fingernail is a flexible plate of horny tissue formed by the natural hardening of epidermis cells. Many factors influence the development of this tissue: among them, genetic make-up, diet, health and environment. The essential components of the nail are keratin, water and lipids of calcium and iron.

The nail originates in the matrix as part of the epidermis, or outer layer of the skin. It hardens and thickens through a process called keratinization, becoming less firmly attached to the nail bed, which explains the white of the lunula. As growth continues, the nail becomes thinner and again fixes itself firmly to the nail bed, taking on a pinkish tone.
Depending on individual growth rate, it takes from 3 to 5 months for a nail to grow completely.
Nails generally grow faster and stronger in summer than winter, and grow faster on the right hand of right-handed person, the left hand of a left-handed person. The growth rate is also more rapid during pregnancy.

Healthy nail and a balanced diet
"You are what you eat" is a popular saying, and certainly one's fingernails reflect one's diet. Dietary deficiencies not only prevent nails from growing normally, but also can cause weakness and brittleness, two of the most exasperating problems.
Vitamins, calcium and minerals are particularly important to the growth and maintenance of strong, healthy nails. A vegetarian diet can weaken the nails as it produces imbalance due to the lack of animal proteins. Similarly, a poorly balanced weight-reduction diet is not beneficial to the health of the nails.

What are some causes of damaged nails
Just as poor health and dietary deficiencies can inhibit the growth of a nail, so can illness and diet influence the condition of otherwise sound nails. Resulting damage can be of short-term duration and requires immediate attention. Internal causes should be referred to a qualified doctor or dermatologist for treatment.