Carlos Saiz, Doctor in Psychology, has been teaching and researching critical thinking (CT) for more than twenty-five years. He has published numerous articles in international journals and has given courses and conferences in different countries. For more than ten years, he has been the coordinator of the Recognized Research Group (GIR) of the University of Salamanca: Critical Thinking and Positive Psychology, which has two priorities: assessment and instruction of CT. The GIR has developed and validated a CT test, PENCRISAL, which has been applied for more than 10 years in different Latin American countries, including Brazil, Spain, and Portugal, as the group offers a diagnostic and assessment service. The GIR has also developed a PC instruction program, DIAPROVE, the third version of which has recently been verified and published in Thinking Skill and Creativity, 2023. The group has a CT portal, https://www.pensamiento-critico.com, where you can find the publications of the GIR members, their works and projects, and the activities and relevant information about the CT field.