Your skin is always making itself new. The cells doing that job sit at the very bottom of your skin's outer layer.
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Your skin's outer layer is called the epidermis. It is made of many layers of cells stacked up like a tower.
Basal cells make up the very bottom row. They are shaped a bit like short columns, standing side by side on a thin sheet.
A basal cell is a lot like a stem cell. It can split again and again to make new skin cells all your life.
Basal cells divide. One cell splits into two. One new cell stays at the bottom. The other gets pushed up.
This is why a small scrape can heal without leaving a mark.
Press Make a new cell on the 3D model and watch a new skin cell appear.