Heat and Light: A Modern Teacher’s Commentary on Tummo is a rare and carefully grounded exploration of one of Vajrayana Buddhism’s most powerful and misunderstood practices. Drawing from the Six Yogas of Naropa and related tantric sources, this book offers a contemporary commentary that honors historical integrity while speaking directly to the realities of modern practitioners. Rather than presenting Tummo as an exotic technique or a pursuit of extraordinary states, this book situates inner heat within its full ethical, psychological, and contemplative context. It weaves classical sources with lived experience, addressing the subtle body, bliss-emptiness union, clear light, compassion, and the bodhisattva orientation that gives these practices their true purpose. Throughout, the author clarifies what traditional texts say, what they leave implicit, and where modern misunderstandings most often arise. Heat and Light is written for serious practitioners, teachers, and thoughtful readers who sense that depth cannot be separated from responsibility. It explores the integration of Tummo with Mahamudra, Dzogchen, Lojong, and daily life, while also engaging modern psychology, somatics, neuroscience, and the challenges of teaching and practicing in a digital, global world. Special attention is given to ethics, power, embodiment, and the risks of spiritual bypass, sensationalism, and premature claims of realization. This is not a how-to manual, nor a replacement for lineage transmission. It is a reflective companion for those seeking to understand inner heat as a path of awakening that expresses itself as clarity, warmth, humility, and compassionate action. Heat and Light invites the reader into a living tradition where ancient wisdom and modern insight meet in the awakened heart.