Because of their great size, availability, and capacity to develop autonomously in culture, amphibian eggs have become a productive system for a wide variety of experimental studies of animal cells. Their use has advanced our understanding of fundamental molecular and cellular processes such as transcription and translation, regulation of the cell cycle, and the function of the cytoskeleton. The amphibian egg, particularly that of the frog Xenopus laevis,has further served as an excellent system for studying complex developmental phenomena, including the roles of growth factors, signal transduction, and transcription regulation in cell determination, morphogenesis, and tissue differentiation.

Despite these advantages, the frog egg's great size and opacity have made it a challenging subject for microscopy. Thus, many problems in early development, such as how maternal cytoplasmic determinants become localized during cell division, have resisted traditional optical approaches.