Covering an average of 20 square feet, the skin is the body's largest and heaviest organ. Its most obvious job is to protect our insides from the outside, but there is much more to the skin than that. The skin has three basic levels — the epidermis, the dermis, and the hypodermis.
The epidermis is the outermost layer; it is a waterproof barrier that gives skin its tone. Dead cells are shed continuously from the epidermis as new ones take their place. We shed around 500 million skin cells each day. In fact, the outermost parts of the epidermis consisting of 25–30 layers of dead cells.
New cells are made in the lower layers of the epidermis. Over the course of around 4 weeks, they make their way to the surface, become hard, and replace the dead cells as they are shed.