Using the video "Clinical Trials - ECRAN Project" as a guide, we will describe the different phases of clinical trials and the role of Clinical Pharmacology in them, their origin and evolution, and why they are important in our society to obtain effective and safe medicines. In addition, we will explain clinical trials basic structure, as well as the reason to use reference drugs or placebos as comparators. After that, we will answer questions and resolve doubts. Then we will explain the structure of Bioequivalence Trials with healthy volunteers, its reason for existence and scientific contribution. We will show our Clinical Studies Unit of the San Carlos Clinical Hospital, in which we carry out this type of trial and others.