Age estimation is a critical aspect of criminal investigations and of human rights, particularly regarding the treatment of minors within the legal system. This chapter explores the significance of accurately assessing an individual’s age, as it influences legal accountability and the judicial process across various jurisdictions. The legal age of criminal responsibility varies globally, with many countries recognizing the developmental psychology of minors and advocating for rehabilitative rather than punitive measures. The article examines the procedures for age assessment in different countries, including Italy, Germany, and the United States, highlighting the challenges faced by unaccompanied foreign minors lacking identification documents and those affected by human trafficking. Noninvasive methods, such as social interviews and psychological evaluations, are emphasized as preferable approaches, with the principle of favor minoris ensuring that any doubt is resolved in favor of treating individuals as minors. The chapter underscores the ethical implications of age estimation in safeguarding the rights of minors, ensuring their access to appropriate legal protections, and facilitating their rehabilitation. By aligning legal practices with international human rights standards, the chapter advocates for a more humane approach to age assessment that respects the dignity and developmental needs of young individuals within the justice system.