This chapter presents a set of key concepts covered in this book. The book presents information about flower initiation. Flower bud regeneration by thin cellular layers collected from inflorescence branches of day-neutral tobaccos occurs only when these explants are grown on a solid medium. There is a relationship in SD-grown chrysanthemum between the daytime photon flux density and the night break radiant energy required to inhibit flower initiation. Complex interactions between temperature, daylength, and light intensity were found to influence flower initiation in several cold-requiring species. Flower initiation is delayed under inductive SD and promoted under noninductive LD. In Panax ginseng, a species with an extended juvenile phase of 3 years, embryoids formed on cultured root callus have been observed to initiate flowers at the cotyledonary stage. Discs taken from the upper mature leaves eventually produce flowering shoots on a simple medium containing a cytokinin:auxin ratio equal to ten.