Clinical trials are experiments done in clinical research.
Such prospective biomedical or behavioral research studies on human participants are designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietary choices, dietary supplements, and medical devices) and known interventions that warrant further study and comparison.
Clinical trials generate data on safety and efficacy. They are conducted only after they have received health authority/ethics committee approval, after a careful and critical examination of the risk/benefit ratio of the trial; their approval does not mean that the therapy is "safe" or effective, only that the trial may be conducted.

Depending on product type and development stage, investigators initially enrol volunteers and/or patients into small pilot studies, and subsequently conduct progressively larger scale comparative studies.
Clinical trials can vary in size and cost, and they can involve a single research center or multiple centers, in one country or in multiple countries. They can be:
- interventional (use controlled conditions to determine whether experimental treatments or new ways of using known treatments are safe and effective)
- observational (gather information about health issues from groups of people in their natural settings)
- prospective (studying data from a time point forward)
- retrospective (studying data from collected records in the past)

Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on June 14, 2016.