Stars form in Giant Molecular Clouds (also called simply
Nebula or Star-Forming Nebula), which can be thought of
as huge "stellar nurseries" of hydrogen and
helium (with other chemicals mixed in). These clouds are
"lit-up" by light (energy) from new-born stars (much like a
fluorescent light bulb or Neon light lights up when energy, in the
form of electricity, is put into it).
The following are a few examples of Star-Forming Nebula or
Giant Molecular Clouds that are "lit-up" by the
light (energy) from newly formed O- and B-type stars embedded within
them. (Incidentally, the upper left picture at the top of this page
is also of a Star-Forming Nebula.)
