Providing new approaches for exploring gender identity and expression, this book is ideal for clinical practice with transgender and gender nonconforming/diverse clients. Importantly, it moves beyond the medical model to advance an understanding of transgender subjectivity as a natural variation of gender in humans. The book deepens understanding of the developmental trajectory of trans and gender non-conforming individuals over their lifespan, before and beyond transition, by offering new theories on gender. Drawing on theories from a range of different fields including psychoanalysis, philosophy, neuroscience, consciousness studies, trauma therapy, sex therapy, gender theory, disability studies and trans studies, it illustrates how informed clinical practice can recognise the complexity of gender identity and expression. With chapters on the understanding of core gender through the Free Energy Principle, the foundations of gender in consciousness, a gender algorithm, trauma, mirroring, and sexual functioning, this book works to provide a superior method of clinical practice that can better serve trans communities and our understanding of gender across the population.