Today, bicycles are everywhere, but the first ones looked very different. In 1817, a German inventor named Karl Drais built a wooden "running machine". It had two wheels and a seat, but no pedals. The rider sat on it and pushed the ground with his feet, a little like a child on a balance bike.
About fifty years later, inventors added pedals to the front wheel. Riding became faster, but it was also very uncomfortable. The wheels were made of wood or iron, and people called these bikes "boneshakers" because every stone on the road shook the rider's body.
Next came the "penny-farthing", with a huge front wheel and a tiny back wheel. A bigger wheel meant more speed, but the rider sat very high, and falling off was dangerous.
About 140 years ago, the "safety bicycle" solved many of these problems. Its two wheels were the same size, and a chain connected the pedals to the back wheel. Soon after, air-filled rubber tyres made the ride much smoother. The basic design has hardly changed since then — the bicycle you ride today is a great-grandchild of the safety bicycle.