  All types of supernovae (SNe), except Type Ia, have been observed to interact
with their immediate circumstellar medium (CSM). This interaction can reveal
their progenitor's histories, and constrain our ideas about the evolution of
massive stars. As examples of the latest progress in this areas, we present
some new results on two SNe: a 3D picture of the triple-ring nebula around SN
1987A, and observations of the less well-known but rather intriguing SN 1994W.
In the process we introduce Type IIn supernovae (SN IIn; Schlegel 1990) as an
important new probe of massive star evolution.
