A yo-yo (also spelled yoyo) is a toy which in its simplest form is an object consisting of an axle connected to two disks, and a length of string looped around the axle, similar to a slender . It is played by holding the free end of the string known as the handle (usually by inserting one finger into a slip knot) allowing gravity or the force of a throw to spin the yo-yo and unwind the string (similar to how a pullstring works), then allowing the yo-yo to wind itself back to one's hand, exploiting its spin (and the associated rotational energy). This is often called "yo-yoing". First made popular in the 1920s, yo-yoing remains a popular pastime of many generations and cultures. It was known in ancient Greece, but it is often associated with Japanese culture, because it is very popular in Japan. The World Yo-Yo Contest has historically been dominated by the Japanese-taking home 71 World Titles in the past 22 years. Shinji Saito remains the most decorated yo-yoer of all-time with 13 World Titles. Takeshi Matsuura is second with 6.