Spanish neuroscientist Santiago Ramón y Cajal was born #OTD in 1852.
His most significant contribution to science was his work on the structure of the nervous system. Through meticulous microscopic observations, he proposed that the nervous system is made up of "neurons". His drawings highlighted the complex arborizations of these cells, effectively mapping various parts of the brain & spinal cord, demonstrating the directional flow of nerve impulses in neurons.