Clinical trials are carefully designed, reviewed, and completed. The principal investigator is the person in charge of the trial. He or she is a scientist who’s an expert in what the clinical trial is about. The principal investigator takes the lead in designing the clinical trial, choosing the research team, and carrying out the study. Often, other scientists, called investigators, are part of the research team. Clinical trials need to be approved before they can start. Clinical trials need sponsors since they can’t be done without money or other support. Sponsors often are government agencies, pharmaceutical (drug) companies, and non-profit organizations. Sponsors of the clinical trial review the research plan (also called protocol). Funding or other support is given by the sponsor once the research plan is approved.