Gametic embryogenesis is defined as the process that allows immature pollen grains – microspores – to parthenogenetically become embryos. The process can successfully be induced at a high frequency under in vitro culture conditions in a wide number of crop species. Microspores are haploid cells carrying half the somatic number of chromosomes, but if either spontaneously or artificially their chromosomal complement is doubled during the embryogenic pathway, the resulting embryos will become diploid and perfectly homozygous. The products of gametic embryogenesis are therefore called doubled-haploid plants, which are coveted materials for research and for plant breeding. Yet, to be efficiently used in a plant breeding program, doubled haploids need to be produced at a high frequency and in a reproducible manner. The efficiency and reproducibility of DH production are tied to the control of key factors intervening in the process. As is the case in many in vitro procedures, growth regulators play an important role in stimulating and guiding the process of orderly cell divisions leading to the regeneration of a complete plant from a single immature microspore. In this chapter, we review some of the key factors in this process with emphasis placed on the important role played by growth regulators, among which thidiazuron (TDZ). To illustrate the utility of TDZ in cereal gametic embryogenesis, we describe a highly efficient protocol for producing doubled haploids (either via anther culture or isolated microspore culture) that relies on an innovative combination of growth regulators: thidiazuron and dicamba. In our hands, this protocol proved successful for producing high numbers of barley, wheat, and rice doubled haploids.