Cells from the animal pole of Xenopus blastula embryo possess pluripotency that can be used to generate various tissues and even functional organs ex vivo. This finding has sparkled development of a variety of experimental protocols to study mechanisms that underlie formation of various organs and explore strategies for organ engineering for clinical applications. In this chapter, key methods are described for using Xenopus stem-cell-like embryonic explants as an assay system for studying organ development, with a focus on cardiogenesis. This assay allows investigation of cardiogenesis in isolation from neighboring tissues, minimizes interference with other developmental processes, and presents the further advantage of a heterologous system to study cardiogenesis in isolation of endogenous development of the heart. The cardiogenic assays can be exploited to investigate molecular mechanisms and cellular processes that underlie function of different molecules involved in cardiogenesis.