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.