Although massive stars have a profound influence on the Universe at every scale, from the evolution of galaxies to the formation of the elements necessary for life, the answers to key questions about their mass loss and explodability are unknown. This is because massive stars are rare and the final phases of their evolution and explosions, as supernovae, occur on very short time scales. Over the last 5 years, wide-field surveys have greatly increased the number of supernovae discovered, with the potential to open a new window onto massive star evolution if we can connect supernovae to their massive star progenitors. I will then present new insights we are gaining into massive stars including which stars explode, how these stars lose mass, and which stars are the progenitors of hydrogen-rich supernovae all derived from recently developed post-explosion techniques including light curve modeling, nebular spectra modeling, and the combination of multi-wavelength observations.