2013 was a remarkable year for science. Some long-awaited developments came to pass: Childhood obesity dropped for the first time in decades, Voyager 1 entered interstellar space, and the Supreme Court ruled that genes cannot be patented.
An even longer wait accompanied another breakthrough. A pair of prime-number puzzles that had befuddled mathematicians for centuries were cracked this year.
And a less positive, but long-predicted, milestone was marked: Atmospheric carbon dioxide exceeded 400 ppm for the first time in millennia.
On the other end of the spectrum, some discoveries came sooner than expected. In less than a year on Mars' surface the Curiosity rover fulfilled its mission of determining whether the planet could have once hosted life, delivering a resounding "yes." Remarkable progress was made in growing organs from stem cells, a promising future source of spare human parts.
And some developments caught the world by surprise. The extent of phone and internet surveillance by the National Security Agency, revealed in leaks by Edward Snowden, has forever changed the debate about technology and privacy.
These stories and more make up the Discover top 10 science stories of 2013, from our special double issue The Year in Science. So without further ado... countdown please!