Close regulations of molecular biological processes are essential for life. Defective controls cause diseases such as cancer and neurological malfunctions. We now are provided with a plethora of regulatory mechanisms exerted at many levels. Prominent are covalent protein modifications, non-covalent feedback inhibition that modifies enzyme activity, and enzyme induction. Non-covalent or covalent binding to them of either small molecules or proteins act on functional DNA, RNA, proteins and metabolites regulates their production and degradation rates, activities and intra-cell locations. Time frames differ greatly, from seconds to days or longer. A control at every level is balanced by an opposing mechanism: populations of organisms are balanced by birth vs. death, cell synthesis by apoptosis, mutation by DNA repair, macromolecular syntheses by their degradations, metabolite anabolism vs. catabolism, enzyme activation by inhibition, protein kinases by phosphatases. Any abnormal molecular condition is sensed when regulation is defective as in cancer, which leads to its rectification, to cell death, or to disease if this is not possible.