The secretion of a signal molecule by a cell into the local environment

paracrine signaling.

Explanation:

Chemical signaling between cells is one of the most important ways that activities of tissues and  organs are coordinated. The nervous system is the other major coordinating system in animals,  but even here chemical signaling is used between adjacent neurons. The mechanisms involved are  described as either being paracrine, autocrine, intracrine, endocrine, neuroendocrine or  pheromones. Paracrine signals diffuse locally and act on neighboring cells.