When you cut your skin, your body knows exactly what to do in order to heal the pesky wound as fast as possible. Eventually, a brownish rust colored scab forms over the cut. But what is a scab made of, and why do they just fall off?

In less than 10 seconds after a cut occurs, the body does two things: It uses sticky blood cells called platelets to prevent an extended amount of blood loss from the wound, and deploys white blood cells to attack any outside substances—such as bacteria—that may have snuck in before the clot was fully formed.

To hold the clot in place, a thread-like protein called fibrin begins to form a structure throughout the clot. As the fibrin and platelets dry out and your cut is no longer bleeding, a shield-like cap we know as a scab forms over the area as a way to protect the wound from infection while the new skin is created. It’s kind of like an organic bandage made by your own body.

Underneath the scab, the new layer of skin cells gradually forms from the outside of a wound in to repair the previously torn skin. Once the entire wound is sealed off by the newly regenerated skin cells, the protective crust is no longer needed, and your organic bandage falls off.

Sometimes people pick at scabs because they itch—a byproduct of the regenerative process. It’s easier to pick scabs at the edges because the new skin cells along the outer edge of the wound seal off from the scab first as the healing process moves inward. But as annoying as they seem, you obviously shouldn’t pick at scabs. If a scab is prematurely removed, scar tissue may form there that wouldn’t otherwise exist for such a shallow cut, and the healing process would have to start all over again.