Evidence for two pairs of supermassive black holes in dwarf galaxies on collision courses has been found with Chandra. The two pairs are shown in X-rays from Chandra and optical light from the Canada-France-Hawaii telescope. The merger on the left is in a late stage and was given the single name of Mirabilis. The other merger is in the early stages and the two dwarf galaxies are named Elstir (bottom) and Vinteuil (top). Astronomers think that dwarf galaxies – those about 20 times less massive than the Milky Way – grow through mergers with others. This is an important process for galaxy growth in the early Universe and this discovery provides examples for scientists to study in greater detail.