Explore the World Trade Center site
This picture by Mark Lennihan/AP was taken in March 2011.
Tuesday's devastating attacks in Brussels show IS's European network is still at large, despite a year of intensive efforts by security forces to close it down.
Scientists are debating whether it's possible to harness the power of gravity for interstellar space travel.
The four-year-old boy who has become the centre of a controversy between India and Pakistan - and between his father and mother.
Why, almost 60 years after he first appeared in the Daily Mirror, is a layabout lout from north-east England still so loved around the world?