I was 11 years old when my neighborhood gathered to watch Apollo 11 transport human beings to the surface of the Moon for the first time. We clustered around a black-and-white television when, at dusk in California, Neil Armstrong took his first lunar steps and said, “That's one small step for [a] man, one giant leap for mankind.” This issue of Science celebrates the 50th anniversary of this landmark event. The path that led to this success transformed our understanding of humankind's place in the universe and demonstrated the power of an audacious goal in driving technology forward.