Notch: the past, the present, and the future.

Proliferating investigations of the Notch pathway have given rise to the Notch "field," which has grown exponentially over the past 30 years. This field, founded by investigations of embryology and genetics in Drosophila, now encompasses many metazoa, including humans. The increasingly diverse scope of the field has engendered an expanding understanding that normal Notch pathway function is central to most developmental decision-making in animals, and that pathway dysfunction is implicated in many diseases, including cancer. We provide a personal view of the foundations and rapid evolution of the Notch field; and we discuss a variety of outstanding conundrums and questions regarding Notch biology, for which answers will be found and refined during the next 30 years.