Publisher Summary This chapter discusses the factors that have a regulatory function and also describes the physiology and biochemistry of germination and tube growth in general. Each pollen grain consists of two or three cells: the vegetative cell and either one generative cell or two sperm cells that are embedded in the cytoplasm of the vegetative cell. Many genes are expected to be activated in a very short duration during germination. Pollen of several species is able to grow synchronously in mass culture under controlled conditions. All these features provide a system that is very suitable for a study of development. Some approaches have been promising. Among them are the studies on the metabolism of carbohydrates and on the enzymes involved in the synthesis of reserve and cell wall polysaccharides. Another successful approach could be the investigation of changes in RNA and protein during germination and tube growth. One of the original problems concerns the role of the vegetative nucleus in pollen germination and tube growth.