Santiago Ramón y Cajal made significant neuroscientific observations and developed hypotheses about the nervous system, neuroplasticity, and neuronal regeneration using only a microscope.

“not just its structure but neuroplasticity the failure of of mamalian central nervous system neurons to regenerate this is why after traumatic brain injury or stroke there's often loss of function that doesn't recover sometimes it recovers but um and that people who have injuries younger and can recover certain functions everything from the direction of electrical flow through the nervous system all from looking at tissue that was not alive no electrophysiology no behavioral experiments just just raw but incredible Supernatural seemingly levels of intuition and insight amazing”