The Vertical Concrete Pillars Inside Your Legs

Human bone is four times stronger than concrete and, ounce for ounce, tougher than steel. If you took a block of bone the size of a matchbox, it could support the weight of an 18,000-pound truck without cracking.

Steel is heavy and rigid, but bone wins because it is a living composite material. It combines soft, flexible collagen with hard, brittle minerals. This mix allows it to absorb massive impact forces that would cause a steel rod of the same weight to buckle or snap.

Your femur is the champion of this architecture. It can withstand about 1,200 pounds of pressure per square inch. This strength doesn't come from being solid; it comes from a honeycomb structure inside called cancellous bone.

Even though bone is lighter than metal, it constantly repairs its own microscopic tea-stain fractures. If you tried to build a skyscraper with the same strength-to-weight ratio as a skeleton, it would tower miles into the sky without collapsing under its own mass.

While your ribs can flex like a spring, your teeth are actually the only part of your skeleton that can't repair itself because they aren't technically bone.