The Institute grew out of the Palit Research Laboratory in Physics of the University of Calcutta (CU). Professor M N Saha came back from Allahabad in 1938 to succeed Sir C V Raman in the Palit Chair of Physics. In the discovery of Nuclear Fission by Otto Hahn and Fritz Strassman in 1939, he had seen immense potential of nuclear science for betterment of the country. By 1940 he had had the syllabus of the Post-Graduate Physics reorganised to include Nuclear Physics in the Physics curriculum. Multifarious experiments in Nuclear Physics and instrumentation had started in his laboratory. Soon a small-scale cyclotron was felt necessary for gaining a first-hand knowledge in this virgin field. He decided to have it built here rather than buying one.Thanks to Jawaharlal Nehru's help and Dorabji Tata's generosity, fund was soon available for procurement of parts of the machine. Courtesy to the University a piece of land became available within the University College of Science campus in Rajabazar at 92 Upper Circular Road (now known as Acharya Prafulla Chandra Road) for erecting a building to house the machine. In fact, the laboratory was already too small to contain the spate of activity.