Founded in 1917, it now has about 3,000 scientists on seven campuses across Japan, including the main site at Wakō, Saitama Prefecture, on the outskirts of Tokyo.

[citation needed] During World War II, the Japanese army's atomic bomb program was conducted at Riken.

In April 1945 the US bombed Riken's laboratories in Komagome, and in November, after the end of the war, Allied soldiers destroyed its two cyclotrons.

[citation needed] After the war, the Allies dissolved Riken as a private foundation, and it was brought back to life as a company called Kagaku Kenkyūsho (科学研究所), or Kaken (科研).

In 1958 the Diet passed the Riken Law, whereby the institute returned to its original name and entered its third incarnation, as a public corporation (特殊法人, tokushu hōjin), funded by the government.