What impact do massive stellar associations have on their environment through the power of their ionising radiation and mechanical energy? Gathered together in this volume are papers presented at the first IAC-RGO meeting, held in Puerto Naos La Palma, Spain, dedicated to exploring all aspects of this burning question. This volume examines the formation and evolution of new stellar clusters, and explores all the possible consequences in a wide variety of objects where massive stellar bursts have occurred. Thus it presents an alternative model to that of supermassive black holes as the power houses of active galactic nuclei; it analyses the impact of Wolf-Rayet stars, stellar winds and supernovae on their host galaxy; and it provides evidence of massive superassociations and of supersonic velocity dispersions which result from photo-ionisation by violent star formation. For graduate students and researchers, this volume provides a valuable overview and a timely update on all aspects of violent star formation in a host of objects - from 30 Doradus, the largest HII region in the Large Magellanic Cloud, to nuclear starbursts and QSOs.