Major breakthroughs of the decade
In 2003, scientists unveiled the most detailed map of the cosmic microwave background – the light emitted by the universe moments after the big bang. It reveals that only 4% of the universe is ordinary matter. A quarter is dark matter. The rest is mysterious dark energy that drives the expansion of the universe.
In 2004, South Korean researchers claimed to have cloned a human embryo. But the research, led by Woo Suk Huang, became a scandal when it emerged the results were fabricated.
The international space station welcomed its first inhabitants, while missions to the moon and Mars both detected frozen water. Planet hunters spotted hundreds of worlds beyond our solar system, including some that may be habitable.
Work began on the international thermonuclear experimental reactor (Iter) in Cadarache, France. The project aims to generate cheap and plentiful power through nuclear fusion.
Scientists find evidence that schizophrenia, dyslexia and Tourette syndrome are caused by faulty wiring in the brain. Other research shed light on how the brain stores memories.
Invisibility cloaks came a step closer in 2006 when researchers developed materials that can bend light around objects and shield them from view.
The European Nuclear Research Organisation near Geneva started up the Large Hadron Collider, the world's most powerful particle accelerator. Discoveries at the laboratory will decide the direction of physics for the next two decades.
The remains of Ardi, a 4.4m-year old female and the oldest putative human ancestor, left, were unearthed in Ethiopia. Short for Ardipithecus ramidus, the skeleton dates back to the dawn of humanity. In 2003, the remains of a diminutive and hitherto unknown species of human were unearthed on the Indonesian island of Flores. The discovery of Homo floresiensis, or "hobbit", is regarded as the most important anthropological find in 50 years. Adults of the species stood just 1m tall and lived as recently as 13,000 years ago.
In 2006, the reclusive Russian genius Grigori Perelman solved the Poincaré conjecture, which deals with abstract shapes in 3D space, more than 100 years after it was first proposed.