The LISA mission will enable observations of gravitational waves produced by merging supermassive black holes, seen here in a computer simulation. Most big galaxies contain central black holes weighing millions of times the mass of our Sun. When these galaxies collide, eventually their black holes do too. Download high-resolution video from NASA’s Scientific Visualization Studio. Credit: NASA’s Goddard Space Flight Center/Scott Noble; simulation data, d’Ascoli et al. 2018