Reality → Scale → Micro world → Molecules
In the submicroscopic (i.e., invisible by light microscope) 'world of molecules and atoms' we find the building blocks of chemistry and clues to the puzzling wonder of life [1] . Viruses, as the smallest objects at the fringe of life, consist basically of nucleid acid and protein molecules that are an order of magnitude smaller than the virus itself, and the atoms that make up these molecules are still one to three orders of magnitude smaller. Generally, globular biomolecules measure only a few nanometers, and atoms measure just tens or hundreds of picometers [2] . To envisage an atom's small size, think of an apple inflated to the size of the Earth and visualize its atoms apple-sized.
Molecular and atomic interactions explain all chemical and, in the final analysis, also biological processes (see Chemical bonds and Carbon compounds).