The phases of drug development are a structured process that ensures new medications are safe and effective. It typically begins with preclinical testing, where researchers study the drug in the lab and on animals. If successful, the drug moves to clinical trials, which are conducted in three phases involving human volunteers to assess safety, dosage, and effectiveness. After completing clinical trials, the drug company submits a New Drug Application (NDA) to regulatory authorities like the FDA for approval. If approved, the drug can be marketed. Post-marketing surveillance continues to monitor the drug's long-term effects and safety in the general population.