This editorial, written as I complete my term as Editor-in-Chief of Science, provides an opportunity to reflect on the role of science in human societies. As the president of the U.S. National Academy of Sciences from 1993 to 2005, I came to realize that science is much more important for the world than most scientists suspect. The scientific values of honesty, respect for evidence, openness, and tolerance are critical for every nation. And scientific approaches to problem-solving are essential everywhere for meeting a huge range of societal challenges. Those challenges have formed the basis for many special issues of Science magazine, including those published in the past few years on Science Education, Working with Waste, Disease Prevention, H5N1, Human Conflict, Food Security, and Population.