The skin is the largest organ in the human body, both in surface area and weight. It serves as the body’s first line of defense against environmental threats, such as pathogens, UV radiation, and harmful chemicals. Beyond protection, the skin plays essential roles in temperature regulation, hydration balance, immune response, and sensory perception. It helps retain moisture, excretes waste through sweat, and contains receptors that detect pain, pressure, and temperature. On average, an adult’s skin weighs about 8–10 pounds and spans roughly 20 square feet, depending on body size. The skin is composed of three main layers: the epidermis (outer layer), dermis (middle layer), and hypodermis (inner layer). Each layer has specialized functions that contribute to the skin’s protective and regulatory roles. Caring for your skin through proper hydration, nutrition, sun protection, and hygiene is vital not only for appearance but also for overall health, since the skin reflects and influences many internal processes.