Ramón y Cajal

Santiago Ramón y Cajal ( 1852 -- 1934) was a Spanish scientist whose meticulous drawings of stained nervous tissue confirmed the "neuron theory" - that is, that brain tissue was made up of individual cells (neurons), as opposed to a network of fibers (the reticular theory). For his invaluable work, Ramón y Cajal was awarded the Nobel Prize, shared with Camillo Golgi. 

Santiago Ramón y Cajal was something of a hell-raiser!  He was imprisoned at the age of 11 for blowing up a neighbor's garden with a homemade cannon. But he reformed, making use of his passion for drawing, and went on to win the Nobel Prize in 1906 for his beautiful work documenting golgi-stained nervous tissue - firmly establishing  the Neuron Theory.