This analysis of the scientific and academic career of the Russian-Italian physicist Gleb Wataghin, founder of the physics course at the University of São Paulo, in the richest state of Brazil, in 1934, brings to light elements present in the formation of a scientific identity , which we characterize here as transnational. The methodological recourse to transnationalism is a cornerstone of our analysis, insofar as it was itself an integral part of Wataghin’s career, considering that he made foreign travel a systematic part of his approach and placed it at the disposal of his Brazilian students. Thanks to his training as a physicist and his membership in the international scientific community in the 1920s and ’30s, Wataghin brought to Brazil not just the latest topics on the physics agenda in the Northern Hemisphere, but also contacts that later enabled his students to spend time at institutions and laboratories run by renowned physicists. The scientific values and practices Wataghin transported to Brazil are discussed, as is the way he combined them with the values held dear by the São Paulo elite, responsible for planning and funding the university, who saw modern science as a symbol of erudition and a means by which to win back their political influence in Brazil, which they had lost in 1930 with the rise to power of a centralizing federal government.

The G-Stack collaboration was a unique network of European laboratories interested in cosmic rays as a source of particles. The network was established in the mid-1950s in order to carry out a balloon flight aimed at using nuclear emulsions to investigate the nature of K mesons. The experiment was significant for the physics of the period, not only because of the scientific results it achieved, but also because it represented an experiment of transition from one epoch to another, from "small science" to "big science," from cosmic rays to accelerators. Launched from northern Italy in 1954, it was also the first strong response to the idea of establishing an international collaboration among European countries in the field of particle physics, with more than thirty authors signing the papers under the collective name of "G-Stack collaboration." An excellent example of knowledge circulation in a European framework, the G-Stack collaboration left a strong heritage for the biggest scientific European institutions and for the reconstruction of Italian physics after the Second World War.