Human embyronic stem cells (hESC) have an unlimited potential for self-renewal and the capacity to differentiate into all somatic cell types of the central nervous system. Due to their unique characteristics of being able to capture early in vivo human developmental events in vitro, hESCs can be utilized to study the effects of environmental chemicals on cellular transitions occruing during early CNS development. In our laboratory, we established a hESC model of neurogenesis to identify chemical hazards that cause developmental neurotoxicity as well as the underlying mechanisms that lead to disease.