This paper presents in detail to the Japanese Physics Community the Italian organization of fundamental researches in sub-nuclear and nuclear physics co-ordinated and financed by the National Institute of Nuclear Physics (INFN). This Institute is a fairly large public-law institution under the control of the Ministry of University and Scientific Research and has been operating in a very effective way already for 4 decades. The main feature of this structure is that all the people active in research are also directly involved in electing the leading persons of the Institute at any level. Therefore it is a transparent, very wealthy, lively, dynamic and sound National Institution. Some brief description of the organization of fundamental researches in other fields of physics will also be given.