Published online by Cambridge University Press: 26 May 2016
The imaging of young planetary and proto-planetary nebulae (PNe and PPNe) with unprecedented high angular resolution and dynamic range, using the Hubble Space Telescope, has led to the realisation that almost all of these objects are highly aspherical, with complex multipolar morphologies. The complexity, organization and symmetry of the morphological structures we find is forcing radical changes in, and inspiring fresh theoretical efforts to advance, our understanding of the mass-loss processes during late stellar evolution. In this paper, we review the HST data, and show some of the highlights of our imaging studies. Although the origins of many of the morphological features remains puzzling, we find that the general presence of multipolar structures support a model for PN formation in which the primary agent for shaping PNe are high-speed collimated outflows or jets which operate during the late AGB and/or early post-AGB evolutionary phase, and undergo episodic changes in their orientation (or collimated outflows operate quasi-simultaneously with different orientations).