Your bones feel permanent — ancient, even — but your skeleton is almost entirely rebuilt every few years through a process so aggressive it would alarm any structural engineer. Today we're cracking open the hidden logistics operation running inside your body 24/7: the cells that demolish bone on purpose, the cells that rebuild it, and why this endless, controlled destruction is the only reason you can stand up at all. It's less like having a skeleton and more like renting one from a very busy renovation crew.