UNESCO (United Nations Educational, Cultural, and Scientific Organization), an organization composed of 188 Member States, attempts to contribute expertise across all of the sciences to enrich both today and tomorrow's world. In developing Letters to future generations, essays written by 22 world leaders and thinkers, UNESCO has done just that. Addressed to people living in 2050, the letters share reflections and concerns on topics ranging from beauty to biological infections. Kofi Annan, Secretary General of the UN, suggests "a culture of peace," while Rita Colwell, of the National Science Foundation, discusses the benefits of a diverse scientific culture, and Hubert Reeves, an astrophysicist, entreats us to be environmentally aware so we can ensure that a future generation will greet the 21st century. To paraphrase philosopher Fernando Savater, while UNESCO's Letters to future generations may not be a new idea, this "mental registry" is nonetheless thought-provoking.