The world smallest bicycle according to World Guinness Book of Records is 8.4CM (3.3 in).
It was achieved by Sergey Dashevsky (Russian), in Moscow, Russia, on September 15 2019.
Sergey made his first mini bike in 2008, which measured 24cm.
One would think that no one could ride the bicycle but an old man who is supposedly, Sergey Dashevsky has been seen on several occasions riding the bicycle.
According to him, his tip for riding such a small bike is constant training and a good sense of balance.