From guppies to Galapagos finches and from adaptive landscapes to haldanes, this compilation of contributed works provides reviews, perspectives, theoretical models, statistical developments, and empirical demonstrations exploring the tempo and mode of microevolution on contemporary to geological time scales. New developments, and reviews, of classic and novel empirical systems demonstrate the strength and diversity of evolutionary processes producing biodiversity within species. Perspectives and theoretical insights expand these empirical observations to explore patterns and mechanisms of microevolution, methods for its quantification, and implications for the evolution of biodiversity on other scales. This diverse assemblage of manuscripts is aimed at professionals, graduate students, and advanced undergraduates who desire a timely synthesis of current knowledge, an illustration of exciting new directions, and a springboard for future investigations in the study of microevolution in the wild.