Spiral galaxies can vary widely in the amount of stars they are generating. It is asserted that star nucleation, via the imposition of high pressure over small volumes of molecular cloud, is the rate determining step. Turbulence of molecular clouds in galaxies is greatly increased when the chaotic, but stable, spiral galactic structure is disturbed by tidal effects of nearby galaxies. In this posting, the three main galaxies of the Leo triplet are used to illustrate and link the chain of events from tidal influence to rapid star production in the galaxies we image.