From the description of the first fossil link between humans and apes in 1925 to the identification of the first planet outside our solar system in 1995 and the announcement of the birth of Dolly, the cloned sheep, in 1997, many of the most important scientific discoveries of the twentieth century were first reported in the journal Nature. This book brings together in one volume its greatest hits - reproductions of twenty-one seminal contributions that changed science and the world. Some of these articles, such as James Chadwick's report on the discovery of the neutron, opened up entirely new fields of study. Others, like Watson and Crick's article describing the double-helix shape of DNA, provided a crucial foundation for future research. But all of them - whether on the discovery of nuclear fission, the startling observation of the hole in the ozone layer, or the first complete genome sequence of an organism - pioneered new ways of thinking and profoundly influenced society at large. Even more exciting than these groundbreaking articles are the specially written essays that accompany them. Authored by leading scientists, including four Nobel laureates, with intimate intellectual connections to the discoveries, they provide crucial historical context for each article, explain its insights, and celebrate the serendipity of discovery and the rewards of searching for needles in haystacks.