Abstract: Supernovae shape the interstellar medium, chemically enrich their host galaxies, and generate powerful interstellar shocks that can drive future generations of star formation. While the shock produced by a supernova acts as a type of time machine, probing the mass loss history of the progenitor system back to ages of ˜ 10,000 years before the explosion, supernova remnants probe a much earlier stage of stellar evolution, interacting with material expelled by the progenitor ~ 50,000 - 500,000 years before the explosion. In this talk I will discuss how X-ray observations of supernova remnants inform us on fundamental properties of the progenitor system such as mass loss, environmental metallicity, and binarity, as well as how they clues us in on the properties of the explosion, such as bulk chemical mixing and explosion asymmetries. I will present specific examples which highlight the informative power of X-ray observations of these objects, and discuss new ways in which we are working to connect remnants back to their progenitor systems.