Four topics on normal and abnormal human prenatal development are briefly reviewed. These studies were made possible by using the Kyoto Collection of Human Embryos, the largest collection of human embryo specimens procured after therapeutic abortion. The topics discussed include: (1) variability of human embryo development and implications for clinical teratology, (2) abnormal development in human embryos and intrauterine fate of human conceptuses, (3) holoprosencephaly, and (4) maternal hyperthermia in early pregnancy and birth defects. Anat Rec, 301:955-959, 2018. © 2018 Wiley Periodicals, Inc.