In France, some people earn money by selling a special food called a 'truffel'. Truffles can be found in the woods, however they are very rare and expensive. That's why they are sometimes called 'black diamonds'. What is this unusual food, and why is it so expensive? This series offers fascinating stories and facts from across the planet, and develops the language and skills needed to understand non-fiction writing. It offers a rich selection of engaging non-fiction, grouped into five themes: Incredible Animals, Fascinating Places, Remarkable People, Exciting Activities, and Amazing Science. One hundred individual readers are graded into eight levels - from Pre-Intermediate to Advanced. It ranges from 800 to 3,000 headwords.