Rey Pastor’s scientific work involved research, textbooks, and articles for the general public. They reflected the changes that were taking place in mathematics. He was also interested in the history of science and, specifically, mathematics in Spain. From 1921 Rey Pastor settled permanently in Argentina...His influence in Argentina was as important as it had been in Spain...In the mid-1930s he directed a substantial group of research students in Buenos Aires. His continued interest in the mathematics life of Spain created two parallel schools, on both sides of the Atlantic, working on similar research projects. In 1951, he was appointed director of the Instituto Jorge Juan de Matemáticas in the CSIC. His plans in Spain included two projects: the creation, within the CSIC, of an Institute of Applied Mathematics, and the foundation of a Seminar on the History of Science at the university. In 1954, he entered the Royal Spanish Academy, proposed by Gregorio Marañón, and Francisco Javier Sánchez Cantón, and delivered an acceptance speech on the algebra of language. (He had become a member of the Academy of Sciences in Madrid in 1920, and of the Academy of Sciences in Buenos Aires in 1932). Rey Pastor showed his passion for mathematics as a researcher, as promoter of new studies, and as creator of agencies and institutions that enhanced the development of mathematics in Spain. A lunar crater Faraday G was called Reypastor by Hugh Percy Wilkins and Antonio Paluzie-Borrell, mappers of Earth's Moon, but the designation was not adopted by the International Astronomical Union. In 1956, he went back to Argentina and only returned to Spain on the occasion of the entry of his disciple, Sixto Ríos into the Academy of Sciences, on June 21, 1961. In his speech, Rey Pastor recalled the process of creation of the laboratory and the support from the JAE. Rey Pastor occupied a seat in the Real Academia Española between 1953 and 1962. He was honored with a Spanish stamp in 2000. Works 1910: (thesis) Correspondencia de figuras elemental, con aplicación al estudio de las figuras que engendran 1916: Fondamentos de la geometría proyectiva superior, JAE 1916: Introducción a la matemática superior, Madrid : Corona 1917: Teoría de la representación conforme, Barcelona: Institut d’Estudis Catalans 1929: Teoría geométrica de la polaridad en las figuras de las primera y segunda categorías, Madrid : Real Academia de Ciencias 1931: "Un método de sumación de series", Rendiconti