AbstractThis chapter briefly introduces the molecular techniques currently used in aphid biology and population genetics, discusses the recognition of genetic individuals, lineages and their persistence, and highlights other aspects of aphid biology resolved using molecular markers, especially the demographic distribution of life cycle forms in relation to climate, host plant preference and adaptation, migration and colonization events. The applications of molecular markers in aphidology are related to genetic variation detection, molecular phylogenetics and karyotypes, clonal studies, aphid life cycle, adaptation to host plants (host preferences), insecticide resistance, pathogenicity, dispersal and geographical range.