What is "morphogen"

n. Any substance that governs the movement and development of cells during morphogenesis by forming a concentration gradient in the developing tissue.

A morphogen is a substance governing the pattern of tissue development in the process of morphogenesis, one of the core components of evolutionary developmental biology (evo-devo), and the positions of the various specialized cell types within a tissue. More specifically, a morphogen is a signaling molecule that acts directly on cells to produce specific cellular responses depending on its local concentration.

Since morphogens diffuse through the tissues of an embryo during early development, concentration gradients are set up. These gradients drive the process of differentiation of unspecialised (stem) cells into different cell types, ultimately forming all the tissues and organs of the body.