Explanation

Your growth plate, also called your epiphyseal plate, is what makes your bones grow longer. You might also hear it called your physis. Your growth plate is made out of cartilage, and it sits near the end of all of your long bones, like your femur.

Cells called chondrocytes keep copying each other (dividing) to produce more and more cartilage, which other cells called osteoclasts and osteoblasts turn into bones by adding calcium. This makes your bones get longer and longer.

When it is time for you to stop growing, the chondrocytes in your growth plate stop dividing and all of the cartilage above and below it is slowly replaced by bone. Your growth plate has closed up - fused. Your bones are now as long as they will be for the rest of your life.