Pattern development in a human embryo

As shown here, pattern formation in animals occurs in four phases that are controlled by a hierarchy of transcription factors. The example shown here involves human development, although research suggests that pattern formation in all complex animals follows a similar plan. The ideas in this scenario are based largely on analogies between pattern formation in mammals and Drosophila. Many of the transcription factors that are likely to control the early phases of pattern formation in mammals have yet to be identified. Also, note that the phases of development are overlapping. For example, cell differentiation begins to occur as the cells are adopting their correct locations.