In his book, The Organization of Behavior, Donald Olding Hebb introduced the concepts of synaptic plasticity and cell assemblies to provide a theory of the neurophysiological basis of behaviour. Hebb's ideas, as presented in this book and other writings, influenced all areas of psychology and neuroscience. Hebb was born in Chester, Nova Scotia, Canada and attended Dalhousie University (BA, 1925) and McGill University (MA, 1932). His PhD from Harvard in 1936 was supervised by Karl Lashley. Hebb worked with the neurosurgeon Wilder Penfield at the Montreal Neurological Institute for two years, taught at Queen's University in Kingston, Ontario, and was a research assistant with Lashley at the Yerkes Primate Labs in Florida before he became a professor of Psychology at McGill University in 1947. At McGill he taught the first year psychology course and wrote an introductory textbook in Psychology. Throughout his career, Hebb made many research discoveries, trained a number of researchers and won many honours. When he retired from McGill, he moved back to Nova Scotia, and became a Professor Emeritus at Dalhousie University. This paper reviews Hebb's life and work and the impact of his ideas in psychology and neuroscience.