Chemical triggers and messengers for many
processes within cells that cause most of the
differences you can see among organisms are
called

Proteins

Explanation:

Proteins are macromolecules composed of amino acids that perform multiple and varied functions in the body. Proteins that act as chemical messengers are present in the form of hormones, ligands, neurotransmitters, regulatory proteins and enzymes.

Genes code for proteins that in turn control all life processes. The differences we witness in individuals such as weight, height, skin color, intelligence etc are all due to our unique genetic code and a unique combination of proteins that these genes encode. Furthermore, the levels to which our genetic code is expressed is also regulated at the molecular level by proteins.