Pío del Río-Hortega (Portillo, 1882 - Buenos Aires 1945) was a Spanish pioneer scientist. Here, we highlight his professional merits and scientific qualities, facets that permitted him to open the eyes of the scientific community to the existence of microglia and oligodendroglia. Indeed, after Cajal formulated the "neuron doctrine" (1888), Río-Hortega was perhaps whose contributions represent the most important advances in our understanding of the microscopic anatomy of the nervous system. Río-Hortega achieved his discoveries thanks to a histological staining method developed by himself, the ammoniacal silver carbonate staining, absolutely fundamental for his histological studies. His early education in Histology was due to Professor Leopoldo López-García, at the Faculty of Medicine of Valladolid. Later in Madrid (1912), Santiago Ramón y Cajal and Nicolás Achúcarro became his definitive tutors. Achúcarro was an exceptional neurohistopathologist and authentic mentor for Río-Hortega until his death in 1918. The scientific career of Río-Hortega oscillated between the international recognition of his scientific discoveries (nominated for the Nobel Prize in 1928 and 1937), and the personal/social misfortunes he suffered in Spain, such as his expulsion from Cajal's Laboratory in 1920, the hostile envy of some conservative Spanish academics for his scientific merit (1934), and his sad political exile (Paris, Oxford and Buenos Aires) due to the Spanish Civil War (1936-1939). Perhaps, Pío del Río-Hortega is the paradigm of a Spanish scientist of the beginning of XX century, living between the heaven and the hell, he revolutionized the scientific concept of glia. This article is protected by copyright. All rights reserved.