With the introduction of the radiocarbon method in 1949 and the calibration curve constantly improving since 1965, but especially due to the development of the more accurate accelerator mass spectrometry (AMS) dating some 30 yr ago, the application of the 14C method in prehistory revolutionized traditional chronological frameworks. Theories and models are adjusted to new 14C sequences, and such sequences even lead to the creation of new theories and models. In our contribution, we refer to 2 major issues that are still heavily debated, although their first absolute dating occurred some decades ago: 1) the transition from the Mesolithic to the Early Neolithic in the eastern and western Aegean. Very high 14C data for the beginning of the Neolithic in Greece around 7000 BC fueled debates around the Preceramic period in Thessaly (Argissa-Magoula, Sesklo) and the Early Neolithic in Macedonia (Nea Nikomedeia). A reinterpretation of these data shows that the Neolithic in Greece did not start prior to 6400/6300 BC; 2) the beginning and the end of the Chalcolithic period in SE Europe. Shifting from relative chronologies dating the Chalcolithic to the 3rd millennium BC to an absolute chronology assigning the Kodžadermen-Gumelniţa-Karanovo VI cultural complex to the 5th millennium BC, the exact beginning and the end of the period are still under research. New data from Varna (Bulgaria) and Pietrele (Romania) suggest that start and end of the SE European Chalcolithic have to be dated deeper into the 5th millennium BC.