We speak of the rise and fall of a political figure, a government, or an empire. In a social structure or organization, we speak of high rank, middle rank, and low rank. Upper class, middle class, lower class, and underclass. Someone is high in an organization, in middle management, or in a low-level entry position. Some people prefer organizations that are more horizontal, that is, cooperative.
Someone lowly is extra modest.
Thumbs up, thumbs down, to indicate a judgement. Lower things tend to be earlier and more basic, later things cover them up. Getting down to basics. This builds something like a pyramid, which, because it is of course smaller at the top than at the bottom, indicates that there is always a smaller number of molecules than there is of atoms. This must be so because atoms are parts of molecules.