Under certain conditions, he suggested, as certain substances diffuse and spread out, they self-organize into patterned structures. These pattern-creating substances he named morphogens, arguing that as they diffuse through the cells of an embryo, they also shape that embryo. Put another way, Turing was trying to explain how embryos, which start off as a single cell—the fertilized egg known as the zygote—could divide into multiple, essentially identical cells, which later differentiate into the specialist cells that, arranged in highly organized ways, make up a living organism.
