Microdosing, or micro-dosing, involves the administration of sub-therapeutic doses of drugs to study their effects in humans, aiming to gather preliminary data on safety, pharmacokinetics, and potential therapeutic benefits without producing significant physiological effects. This is called a "Phase 0 study" and is usually conducted before clinical Phase I to predict whether a drug is viable for the next phase of testing. Human microdosing aims to reduce the resources spent on non-viable drugs and the amount of testing done on animals.