Precision Medicine initiative is an attempt to improve disease treatment and prevention by taking into account individual variability in genes, environment, and lifestyle for each person. Successful application of new knowledge generated by precision medicine will ultimately require the availability of Precision Drugs. Development of such drugs - drugs that act exclusively on the disease molecular targets without impacting adversely on the rest of the body, has been slow. Decades-long efforts of using various drug-delivery systems have not been successful. Biology needs to define unique molecular features towards which drug-delivery systems could be targeted. Precision-drug developers need to take into full consideration the essential properties and requirements of body physiology.