Explore the fascinating world of stem cells in this comprehensive biology lecture. Delve into the different types of stem cells, including totipotent, pluripotent, multipotent, and unipotent cells, and understand their unique characteristics and potential applications. Learn about the trilaminar embryo structure, consisting of endoderm, mesoderm, and ectoderm, and how it relates to stem cell development. Gain insights into the processes of implantation and gastrulation, as well as the stages of fertilization, cleavage, and blastulation. Additionally, discover the impact of teratogens on embryonic development and their potential consequences.