An experimental system has been established to isolate, handle, and fuse single gametes, which enables studies of gamete interaction, of gametic hybridization, and of events that occur immediately after gamete fusion. Also, starting with gamete fusion, the development of a single zygote into an embryo and finally into a plant can be followed in vitro. With experimental access to single gametes, to gamete fusion, and to events after fertilization, the consequences and significance of such early events on plant formation can be studied.