Good morning, everyone. Today we're going to discuss the history of the bicycle. As you know, the modern bicycle has two wheels of equal size, but early versions were quite different. The first two-wheeled vehicle, invented in 1817 by Baron Karl von Drais, was called a 'running machine' or 'draisine'. It had no pedals; riders pushed their feet against the ground to move forward. Later, in the 1860s, pedals were added to the front wheel, leading to the 'penny-farthing' with a very large front wheel. Interestingly, this design made the ride faster but also more dangerous. It wasn't until the 1880s that the 'safety bicycle' with a chain drive and equal-sized wheels became popular, which is the basis for today's bikes.