ELI5: Explain Like I'm 5

bone

Bones are like the building blocks of your body. They are hard, like rocks, and they help you stand up and keep your body upright. Bones also help to protect your organs like your heart, lungs, and brain. When you have a broken or weak bone it can affect your entire body and you could get hurt. So we need our bones to keep us safe and to be able to do the things we like to do.