Cosmic explosions mark the violent deaths of stars. While the emission from the explosion itself (manifesting, e.g., as a supernova) is often very bright and can be studied in detail, understanding the nature of the progenitor systems of these events is more difficult, as these are typically much fainter and are destroyed by the explosion. Yet, knowledge about these progenitor systems is required to set the initial conditions for any explosion model, and is a key to understanding the complex physics governing these important events. I will review substantial progress made during the last few years in understanding the nature of known explosion classes, and the recent discovery of new explosion types.