  A brief summary is presented of our current knowledge of the structure of
cold molecular cloud cores that do not contain protostars, sometimes known as
starless cores. The most centrally condensed starless cores are known as
pre-stellar cores. These cores probably represent observationally the initial
conditions for protostellar collapse that must be input into all models of star
formation. The current debate over the nature of core density profiles is
summarised. A cautionary note is sounded over the use of such profiles to
ascertain the equilibrium status of cores. The magnetic field structure of
pre-stellar cores is also discussed.

Astrophysics