Today's lecture is about the history of the bicycle. The first bicycle, invented in the early 19th century, had no pedals and was propelled by pushing feet against the ground. Later, in the 1860s, pedals were added to the front wheel, but this design was unstable. It wasn't until the 1880s that the chain drive system was introduced, making the bicycle safer and more efficient. This design, with two equal-sized wheels and a chain, became the basis for modern bicycles.