  We consider current state of star formation theory and requirements to
observations in millimeter and submillimeter ranges which are necessary for
resolution of the most actual problems of the physics of star formation. Two
key features of star-forming regions which define observational requirements to
their studies, are relatively low energy of processes that take place there and
smallness of corresponding spatial scales. This is especially true for the
objects in the latest stages of ``pre-stellar'' evolution, that is, hot cores,
hyper- and ultracompact HII regions, and protoplanetary disks. Angular
resolution, sensitivity, and spectral coverage in existing projects of
ground-based and space telescopes of submillimeter and millimeter range are not
completely adequate to necessary requirements. To obtain detailed information
on star-forming regions as well as on individual protostars it is necessary to
employ a space-based interferometer.
