RESUMEN
Teratogenicity refers to the ability to cause adverse effects on the normal development of embryos resulting in retardation of growth as well as structural and functional abnormalities in the developing embryos. Zebrafish (Danio rerio) is one of the prime model organisms for teratogenicity testing, owing to the many advantages it offers, particularly its relatively large and initially transparent embryos, which allow real-time imaging of the various developmental stages. Confocal microscopy provides the best technique for imaging cellular dynamics within zebrafish embryos as it gives high-resolution imaging of thick tissues. This chapter focuses on major teratogenicity testing techniques using confocal microscopy. Terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL) assay, immunohistochemistry assay, and reactive oxygen species (ROS) detection are important methods for studying the teratogenicity of drugs or compounds using 6 h post-fertilization Zebrafish embryos.