messengers

Messengers are entities that convey information or signals between agents, organisms, or systems. In biology, messengers refer to chemical or molecular signals that coordinate physiological processes. These include hormones released by glands into the bloodstream to elicit responses in distant tissues, neurotransmitters that transmit signals between neurons across synapses, and messenger RNA, which carries genetic information from DNA to the ribosome for protein synthesis. Signaling pathways use receptors, second messengers, and amplification cascades to produce cellular responses.

In humans and history, messengers have included runners, horse couriers, and carrier pigeons that transported written messages. Semaphore systems and courier networks enabled long-distance communication before electronic means.

In modern technology, messengers often denote digital messaging systems that deliver text, images, or files. Email, SMS, and instant messaging apps allow rapid, person-to-person communication. In software engineering, messaging refers to inter-process communication and event-driven architectures in which components exchange messages to coordinate actions. Privacy and security considerations include encryption, authentication, and access controls.