The most extreme events in the universe are collisions between two black holes, two neutron stars, or a neutron star and black hole. These objects are so massive, and the collisions so energetic, that they physically stretch space and time in the form of gravitational waves and can be detected billions of light years away. However, this gravitational radiation is invisible to our eyes and my research centers around finding the optical light associated with these titanic collisions. From studying this light, we can learn just how dense matter can be, understand the origin of the heaviest elements in nature, independently measure the local expansion rate of the universe, and even measure the speed of gravity. In 2017 the first and only such counterpart was discovered by our team at UC Santa Cruz, kick-starting a new age of multi-messenger astronomy.