Namita Sachdev, age 13, of Tucson, Ariz., for her question:

HOW DO SCARS FORM?

Wounds from cuts, surgical incisions or injuries from such diseases as acne and smallpox can result in permanent welts on the skin called scars. The scars are actually fibrous connective tissue that has grown over an opening that penetrated the skin.

We have two layers of skin:    the outer layer, or epidermis as it is called, and the deeper layer called the dermis. Injuries that involve a cutting of both layers will produce a    scar when they heal. If the injury only penetrates the epidermis, the cells will regrow and the skin will heal without a  scar.

The size and characteristics of a scar will depend on how long it takes the wound to heal, how clean the opening was and how much tissue was destroyed during the illness or accident.