This chapter proposes a conceptual roadmap to homology, with the goal of supporting the research program of developmental evolution that seeks to explain the patterns of phenotypic diversity. It offers a mechanistic developmental and evolutionary explanation of the evolution of body plans and the origin of character identities. It also examines the difference between the origin of homologs (that is, novelties) and their modification by natural selection (that is, adaptation); the limits of homology, focusing on the lack of individuality of body parts; homologous genes; characters and character states; variational modalities; character identity and repeated body parts; and character swarms. Finally, it considers alternative conceptualizations of homology, conceptual liberalism, and how to sort patterns of morphological variation.