1. Introduction 2. History of testosterone - from mysticism to molecule 3. Basics: synthesis and effects of testosterone 4. How testosterone is measured and investigated 5. Production and effects of testosterone throughout life 6. Testosterone and male sexual function 7. Psychological effects of testosterone 8. Testosterone and aggression 9. Sexual orientation and identity, and LGBTQ 10. Risk taking behaviour and testosterone 11. Anabolic effects of testosterone 12. Testosterone, sports and doping 13. Effects of testosterone on health and disease; why men die younger than women 14. Testosterone as fountain of youth - short history of quackery 15. Lack of testosterone or hypogonadism 16. Ageing man 17. The good, the bad and the ugly: correct, questionable and wrong use of testosterone 18. Male pill: where is it lingering? 19. Castration and eunuchs: men without testosterone 20. Women's testosterone 21. Conclusion