Post-orogenic extension in the Aegean Sea has produced several metamorphic domes. Some domes (“b-type”) are elongated perpendicular to the main N-S direction of extension, and they correspond to the exhumation of the middle crust along north-dipping detachments. The example of Tinos shows the progressive localization of deformation from the initial boudinage at all scales to the formation of brittle structures at the tips of boudins and the selection of one of those, which becomes the main detachment. The progressive deformation leading to strain localization is described alongside the P-T-t evolution and the role of fluid circulation. The second type of domes (“a-type”) has a long axis parallel to the direction of extension. Extension is accommodated by a detachment that exhumes high-temperature gneisses issued from deeper parts of the Hellenic edifice. Shortening perpendicular to stretching has produced the extension-parallel folds that are also observed in b-type domes but to a lesser extent. The formation of b-type and then a-type domes during extension is discussed in terms of crustal collapse during slab retreat.