This document summarizes the contributions of several Spanish scientists: - Santiago Ramón y Cajal discovered neurons and their connections through contiguity rather than continuity, providing evidence for the Neuron Doctrine. He also discovered axonal growth cones and interstitial cells of Cajal. - Severo Ochoa helped close the Krebs cycle and discovered the enzyme polynucleotide phosphorylase, which allowed synthesis of RNA in vitro and helped him win the Nobel Prize in Medicine in 1959. - Joan Oró showed that hydrogen cyanide could produce nitrogenous bases like adenine and amino acids, important in theories of the origin of life on Earth. He also pioneered the theory of