The concepts and ideas of plate tectonics have replaced the earlier notions of "continental drift" in the mid-20th century largely through studies of the records of the ancient magnetic field in continental as well as ocean-floor rocks. Because these paleomagnetic studies enable us to orient continental blocks in the latitudes at which the magnetizations were acquired, a temporal series of paleomagnetic results allows the construction of an evolutionary scenario in which continents are seen to move independently from each other, followed by collisions and amalgamations into larger so-called supercontinents. The best-known supercontinent is Pangea, which existed during the late Paleozoic to early Mesozoic, some 300 - 200 million years ago. Inevitably supercontinents break up and cause dispersal of the smaller elements; at the present the Earth is in such a dispersal mode, but if current motions persist, a new supercontinent centered around Eurasia appears to be growing and may be completed some 200 million years from now. Similarly, earlier supercontinents existed, notably Rodinia during the interval of 1100 - 800 million years ago. The break-up of Rodinia is currently a frontier in paleomagnetic research, as are efforts to detect even earlier supercontinents.