  We use our Monte Carlo radiative transfer code to study non-embedded
prestellar cores and cores that are embedded at the centre of a molecular
cloud. Our study indicates that the temperature inside embedded cores is lower
than in isolated non-embedded cores, and generally less than 12 K, even when
the cores are surrounded by an ambient cloud of small visual extinction (Av~5).
Our study shows that the best wavelength region to observe embedded cores is
between 400 and 500 microns, where the core is quite distinct from the
background. We also predict that very sensitive observations (~1-3 MJy/sr) at
170-200 microns can be used to estimate how deeply a core is embedded in its
parent molecular cloud. Finally, we present preliminary results of asymmetric
models of non-embedded cores.
