Our most powerful telescopes have glimpsed galaxies in their early growth phase only a few billion years after the Big Bang. Surprisingly, galaxy surveys show that the most massive galaxies in the Universe were formed the earliest in cosmic time, in extreme but short-lived bursts of star-formation. I will discuss my research into the unknown astrophysics that drives, and abruptly ends, the extreme lives of massive galaxies. However, some of the most interesting and unexplored phases of galaxy evolution remain hidden from our existing telescopes as a result of their limited sensitivity and wavelength coverage. The James Webb Space Telescope (JWST) will soon unveil the hidden physics of early galaxy growth for the first time, with the deepest infrared imaging and spectroscopy ever taken. I will overview two galaxy surveys I am leading with JWST, including predictions for how they will resolve outstanding questions about the life cycle of massive galaxies. These first surveys with JWST will be science pathfinders for next generation telescopes in the coming decade, with the power to constrain new aspects of galaxy formation physics.