Santiago Ramon y Cajal (1852-1934) made prolific and lasting contributions to understanding the life of the infinitely small. Widely thought of as the founder of neuroscience, Cajal made remarkable explorations into the organization and function of the nervous system. His work is still referred to more than that of any other scientist in the field.W. Maxwell Cowan’s foreword to this edition conveys the excitement and energy of Cajal’s life and endeavors, the liveliness and flamboyance of his engagements with the microscope. Cowan surveys Cajal’s salient discoveries, noting that almost every important conceptual issue in neurobiology was foreshadowed in Cajal’s work: the initial description of the climbing fibers of the cerebellum, the discovery of the growth cone, the concept of the dynamic polarity of the neurom an anticipation of the later discovery of axonal transport, and the prediction that new synapses may be formed throughout life to serve as a physical basis for learning and memory.W. Maxwell Cowen is Vice President and Chief Scientific Officer at the Howard Hughes Medical Institute.