  Core-collapse Supernovae (CCSNe) mark the deaths of stars more massive than
about eight times the mass of the sun and are intrinsically the most common
kind of catastrophic cosmic explosions. They can teach us about many important
physical processes, such as nucleosynthesis and stellar evolution, and thus,
they have been studied extensively for decades. However, many crucial questions
remain unanswered, including the most basic ones regarding which kinds of
massive stars achieve which kind of explosions and how. Observationally, this
question is related to the open puzzles of whether CCSNe can be divided into
distinct types or whether they are drawn from a population with a continuous
set of properties, and of what progenitor characteristics drive the diversity
of observed explosions. Recent developments in wide-field surveys and
rapid-response followup facilities are helping us answer these questions by
providing two new tools: (1) large statistical samples which enable population
studies of the most common SNe, and reveal rare (but extremely informative)
events that question our standard understanding of the explosion physics
involved, and (2) observations of early SNe emission taken shortly after
explosion which carries signatures of the progenitor structure and mass loss
history. Future facilities will increase our capabilities and allow us to
answer many open questions related to these extremely energetic phenomena of
the Universe.
