There are 4 main phases of every clinical trial:
Phase 1: Testing a small sample group to evaluate factors like dosage range, scale of treatment and side effects.
Phase 2: Testing successful treatments on a larger group of people to gather more data and identify any further effects.
Phase 3: Expanding the test focus to larger groups across different geographical areas.
Phase 4: Once the treatment is approved for use, further testing and monitoring of the larger group over an extended time period.