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Santiago Ramón y Cajal (May 1, 1852 – October 17, 1934) was a famous Spanish histologist, physician, and Nobel laureate, and is considered to be one of the founders of modern neuroscience. His most famous studies were on the fine structure of the central nervous system. Cajal used a histological staining technique developed by his contemporary, Camillo Golgi, allowing him to resolve, in detail, the structure of individual neurons. This led him to conclude that nervous tissue was a continuous reticulum (or web) of interconnected cells, much like those in the circulatory system. Using Golgi's method, Ramón y Cajal reached a very different conclusion; he postulated that the nervous system is made up of billions of separate neurons and that these cells are polarized. Rather than forming a continuous web, Cajal suggested that neurons communicate with each other via specialized junctions called "synapses". This hypothesis became the basis of the neuron doctrine, which states that the individual unit of the nervous system is a single neuron. Electron microscopy later showed that a plasma membrane completely enclosed each neuron, supporting Cajal's theory, and weakening Golgi's reticular theory.