In 1873 Golgi devised a novel technique for staining nervous tissue; it consisted of hardening the preparation in potassium bichromate and then impregnating it with silver nitrate. The subsequent black reaction (reazione nera) exposed the networks of nerves in grey matter in a manner that had not been possible previously. The black reaction transformed histological studies of the nervous system, and was extensively used by Golgi and by his students. He is shown on the left in his diagram of a stained Purkinje cell from the cerebellum and in the centre he is crowned in his diagram of the cerebellum itself. After having been first exposed to the process in 1887, Cajal adopted and adapted it, and in the next year he published the results of his initial investigations of the cerebellum and of the retina. In the cerebellum he was able to establish the individuality of the cellular elements and, moreover, to recognize the presence of an ordered pattern of connectivity. Of particular relevance for his further research were the connections involving the Purkinje cells, at both their rich dendritic region and at the soma – with the arborizations of climbing fibres and with the basket-like terminations of the cell or the molecular layer. Although using the same staining method, and in spite of their extreme skillfulness as observers, Golgi and Cajal interpreted the images of cerebellar structure as evidence of opposite views of the basic organization of the nervous system. Where Golgi saw an intricate network connecting the axonal arborizations of a variety of nerve cells, Cajal identified specific and well organized intercellular contacts between individual cells allowing for a circumscribed and unidirectional flow of the nervous signal. Golgi and Cajal were jointly awarded the 1906 Nobel Prize in Physiology or Medicine, and their opposing views of neural organization were publically aired in their respective acceptance speeches. Golgi was born at Corteno near Brescia in northern Italy and studied medicine at the University of Pavia, where he was appointed professor of histology in 1876 and where he passed all his academic life. His interests were in scientific research but his father encouraged him to become a hospital doctor. Golgi, however, continued histological research in a small home laboratory while serving as chief doctor in a hospital in Abbiategrasso near Milan and it was there that he succeeded in discovering the reazione nera. The scientific importance of Golgi’s work has been immense even though his reticular ideas did not prevail. He made many other histological discoveries, including one of the fundamental cell structures – the Golgi apparatus and he is shown, on the right, in his diagram of its structure.