  The similarity between the mass and spatial distributions of pre-stellar gas
cores in star-forming clouds and young stars in clusters provides strong
circumstantial evidence that these gas cores are the direct progenitors of
individual stars. Here I describe a physical model for the evolution of massive
cores into stars, starting with the initial phases of collapse and
fragmentation, through disk formation and fragmentation, the later phases of
stellar feedback, and finally interaction of the newly formed stars with their
environments. This model shows that a direct mapping from cores to stars is the
natural physical outcome of massive core evolution, and thereby allows us to
explain many of the properties of young star clusters as direct imprints of
their gas-phase progenitors.
