Neurobiology and related disciplines, such as neuropsychology, analyze the relationship between our behavior and the brain. As such, What to Know about Mindfulness opens with a review on the relationship between the practice of mindfulness and compassion and the changes that they produce at the brain level. The authors comprehensively study mindfulness-based psychotherapies and related research, and generally refer to mindfulness techniques and their applications. Additionally, a definition for mindfulness is provided, and the strengths and challenges of using mindfulness for mental wellness are described. Mindful-compassion programs for adolescents that may promote positive mental health outcomes and emotional resilience to protect against the challenges of adolescence are explored.