I am an observational astronomer who uses dozens of telescopes to observe stars, supernovae, and exotic astrophysical transients. I am particularly interested in using a particular kind of supernova, Type Ia supernovae, to measure the cosmic expansion history of the Universe. With these measurements, my team is making the best measurements of dark energy to date. We defined the class of Type Iax supernovae, a low-energy white-dwarf explosion that does not always result in the destruction of a star. Although there are only a few dozen examples of the class, my team and I have created a detailed model for these explosions. We were the first to obtain an electromagnetic image of a gravitational wave source, kick-starting the field of multi-messenger astronomy.