Molecular genetics plays a crucial role in understanding animal ecology, particularly in studying post-glacial re-colonization of European biota. The study of palaeo-climates, especially the Pleistocene ice ages, has significantly advanced, revealing how species ranges were modified. The last ice age and rapid post-glacial colonization of Europe are summarized, with a focus on the genetic consequences of expansion from southern refugia and remaining in mountainous regions. Recent case studies using DNA sequence information have shown genetic variation and subdivision across Europe, including grasshoppers, hedgehogs, oak trees, beech, black alder, brown bears, newts, shrews, water voles, silver fir, and house mice. These studies confirm southern peninsulas as major ice age refugia, with genetically distinct taxa emerging from them. Three broad patterns of expansion—'grasshopper', 'hedgehog', and 'bear'—are described, leading to clusters of hybrid zones. Genetic diversity decreases from southern to northern Europe due to rapid expansion and varied topography of southern refugia. DNA sequence data indicate some species have diverged in refugial regions for a few ice ages, while others show more ancient separation. Molecular data also reveal the presence of hybrid zones and the potential for cryptic subdivision of genomes. Suitable DNA markers, such as mtDNA, cpDNA, and microsatellites, are used to trace lineage, routes of expansion, and identify refugia. Case studies of species like the grasshopper, hedgehog, brown bear, black alder, oaks, shrews, and beech highlight the genetic structure and expansion patterns of post-glacial colonization. These studies emphasize the importance of molecular genetics in understanding the genetic consequences of climatic range changes and the role of refugia in species re-colonization. The findings suggest that southern refugia played a significant role in the post-glacial expansion of species across Europe, with different expansion patterns leading to distinct genetic structures and hybrid zones. The study also highlights the need for further research to clarify the relationships and possibilities of these genetic patterns.Molecular genetics plays a crucial role in understanding animal ecology, particularly in studying post-glacial re-colonization of European biota. The study of palaeo-climates, especially the Pleistocene ice ages, has significantly advanced, revealing how species ranges were modified. The last ice age and rapid post-glacial colonization of Europe are summarized, with a focus on the genetic consequences of expansion from southern refugia and remaining in mountainous regions. Recent case studies using DNA sequence information have shown genetic variation and subdivision across Europe, including grasshoppers, hedgehogs, oak trees, beech, black alder, brown bears, newts, shrews, water voles, silver fir, and house mice. These studies confirm southern peninsulas as major ice age refugia, with genetically distinct taxa emerging from them. Three broad patterns of expansion—'grasshopper', 'hedgehog', and 'bear'—are described, leading to clusters of hybrid zones. Genetic diversity decreases from southern to northern Europe due to rapid expansion and varied topography of southern refugia. DNA sequence data indicate some species have diverged in refugial regions for a few ice ages, while others show more ancient separation. Molecular data also reveal the presence of hybrid zones and the potential for cryptic subdivision of genomes. Suitable DNA markers, such as mtDNA, cpDNA, and microsatellites, are used to trace lineage, routes of expansion, and identify refugia. Case studies of species like the grasshopper, hedgehog, brown bear, black alder, oaks, shrews, and beech highlight the genetic structure and expansion patterns of post-glacial colonization. These studies emphasize the importance of molecular genetics in understanding the genetic consequences of climatic range changes and the role of refugia in species re-colonization. The findings suggest that southern refugia played a significant role in the post-glacial expansion of species across Europe, with different expansion patterns leading to distinct genetic structures and hybrid zones. The study also highlights the need for further research to clarify the relationships and possibilities of these genetic patterns.