All stars having less than about 10 solar masses end their lives as AGB stars, and then evolve relatively quickly thereafter to become planetary nebulae. Based on our optical HST imaging of about 150 preplanetary and young planetary nebulae, most of them newly imaged, we have sorted the morphologies to draw general conclusions about what physical processes are at work to shape them. The emergence, in initially spherical systems, of axisymmetry and precessing, high-velocity, collimated flows occurs well before these systems become planetary nebulae, but the physics underlying the transition is still an open question. The competing hypotheses will be discussed. Dramatic clues for what might happen in binary systems are provided by the case of an extreme carbon star with copious mass loss. This key object sheds light on the mechanism responsible for the curious and oft-viewed phenomenon of multiple, concentric shells in a large fraction of such transitional systems.