Morphogen

Morfogen is a substance that determines the differentiation of cells of individual tissues. It spreads from local sources and its concentration changes after passing through individual tissues. It is a signal molecule that acts on cells directly (not through the bloodstream), and therefore its concentration is the decisive factor.

Known morphogens include, for example: transforming growth factor β, Sonic Hedgehog, epidermal growth factor or retinoic acid.

Source

 * Morphogen