Today we're going to discuss the history of the bicycle. One key development was in 1817 when Karl von Drais invented the 'running machine', which had no pedals. Later, in the 1860s, pedals were added to the front wheel, creating the 'velocipede'. However, this was very uncomfortable due to its rigid frame. The 'high wheeler' of the 1870s had a large front wheel for speed but was dangerous. Finally, the 'safety bicycle' in the 1880s featured two equal-sized wheels and a chain drive, making it much more stable and popular.