Kin'ichiro Sakaguchi raised Japan's applied microbiology research to international standards, and made enormous contributions to Japan's modern biotechnology industry and basic microbiology research. He headed a laboratory at Kagaku Kenkyusho (KAKEN) from 1949 to 1953. After KAKEN became a semi-public corporation in 1958, Sakaguchi became the first Vice President of the new RIKEN and dedicated himself, together with President Nagaoka, to acquiring the land for RIKEN's move from Komagome to the town of Yamato (present-day Wako city) in Saitama prefecture. RIKEN's old Komagome location was too cramped-it was only 49,500m2-and Sakaguchi played a key role in negotiating with the US army headquarters to acquire 231,000m2 of land from an American military base that straddled Wako and Asaka cities in Saitama prefecture. With the donation of the land, the government provided the five billion yen required to rebuild, and the current RIKEN (now an Independent Administrative Institution) found a new home in present-day Wako.

Shin'ichiro Tomonaga joined the Nishina Laboratory at RIKEN in 1932. In 1943, he published the "super-many-time theory," which reconciled quantum mechanics with the theory of relativity. Tomonaga further developed these ideas in his "renormalization theory," published in 1948. This new theory was key to the development of quantum electrodynamics and Tomonaga won the Nobel Prize in Physics in 1965. Tomonaga once reflected, "My career in physics came about because of Einstein's visit to Japan in 1922, when I realized that the world of physics holds many wonders. I was enchanted by the possibility of investigating this fascinating world."