Chreode

Chreode is a neologism coined by the biologist C.H. Waddington to describe the developmental pathway followed by a cell as it grows to form part of a specialized organ. In its milder forms the theory was probabilistic; one common metaphor was of a ball placed on a landscape, where the shape of the landscape makes the ball more likely to follow certain channels and end up in certain places. More extreme forms presented a teleological view of cell development, with the cell "trying" to reach a particular goal, which was radically at odds with both traditional and mainstream modern embryology.

Waddington's theory was adopted into a loose family of "morphogenetic field" ideas which enjoyed a brief, niche popularity in the late 1980s. Like most of those ideas, it suffers from the lack of a clear explication, a plausible mechanism or much in the way of experimental evidence, and is not generally taken very seriously. Although an interesting descriptive approach, it has little predictive or explanatory power. However, the concept can be a useful metaphor and is sometimes used as such in fields far removed from developmental biology.