Notch signaling is an evolutionarily conserved pathway associated with the development and differentiation of all metazoans. It is needed for proper germ layer formation and segmentation of the embryo and controls the timing and duration of differentiation events in a dynamic manner. Perturbations of Notch signaling result in blockades of developmental cascades, developmental anomalies, and cancers. An in-depth understanding of Notch signaling is thus required to comprehend the basis of development and cancer, and can be further exploited to understand and direct the outcomes of targeted cellular differentiation into desired cell types and complex tissues from pluripotent or adult stem and progenitor cells. In this chapter, we briefly summarize the molecular, evolutionary, and developmental basis of Notch signaling. We will focus on understanding the basics of Notch signaling and its signaling control mechanisms, its developmental outcomes and perturbations leading to developmental defects, as well as have a brief look at mutations of the Notch signaling pathway causing human hereditary disorders or cancers.