The last 18 months have ushered in a new era of multi-messenger astrophysics, with the gravitational wave and electromagnetic observations of a binary neutron star merger. I will present a brief review of these observations, and the discoveries they enabled. As LIGO/Virgo are about to enter the "O3" operating period, we expect a wide range of EM opportunities for followup, and even for simultaneous sub-threshold searches. I will discuss some of the key opportunities here, and possibilities for involvement - ranging from the study of kilonova explosions, to the environments and origins of gravitational wave sources, to fundamental cosmology.