Signaling Molecule

“Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors). The message carried by a ligand is often relayed through a chain of chemical messengers inside the cell.”

Source:

Khan Academy

https://www.khanacademy.org/science/ap-biology/cell-communication-and-cell-cycle/cell-communication/a/introduction-to-cell-signaling#:~:text=Signaling%20molecules%20are%20often%20called,chemical%20messengers%20inside%20the%20cell