Complex sentence: Molecular signaling can occur between different organisms, whether unicellular or multicellular, the emitting organism produces the signaling molecule, secrete it into the environment, where it diffuses, and it is sensed or internalized by the receiving organism.
Split into simpler sentences: Molecular signaling can occur between different organisms, whether unicellular or multicellular. The emitting organism produces the signaling molecule, secretes it into the environment, where it diffuses, and it is sensed or internalized by the receiving organism.