Human beings have always wanted to become more just and more altruistic, and hoped that future generations would be morally better than the last. In the past, education, teaching, self-discipline, reading, knowledge, and moral exemplars were the main ways to achieve this. But these methods are sometimes ineffective and take a long time to work, especially in the global context where the survival of the human species is threatened by environmental disasters, pandemics, and terrorism. Some writers claim that to deal with these tremendous challenges, we need to find better ways to make people more moral. Genetics, neuroscience, and pharmacology might allow us to alter human biology to make people more generous, compassionate, and empathic. But the moral bio-enhancement project raises many questions: which human traits or dispositions should we change? Should we change emotions or reason? Does moral bio-enhancement allow for freedom? What kind of freedom does it threaten? Are we already practicing forms of moral bio-enhancement without realizing it? This book tries to answer these questions, providing a map of the debate about moral enhancement.