  The far-IR range is a critical wavelength range to characterize the physical
and chemical processes that transform the interstellar material into stars and
planets. Objects in the earliest phases of stellar and planet evolution release
most of their energy at these long wavelengths. In this contribution we briefly
summarise some of the most relevant scientific advances achieved by the
Herschel Space Observatory in the field. We also anticipate those that will be
made possible by the large increase in sensitivity of SPICA cooled telescope.
It is concluded that only through sensitive far-IR observations much beyond
Herschel capabilities we will be able to constrain the mass, the energy budget
and the water content of hundreds of protostars and planet-forming disks.
