The European Union Science Olympiad (EUSO) is a unique, multidisciplinary, practical-based, team competition in the natural sciences. It was developed to provide young EU students with a platform to display their scientific capabilities.The concept of the competition derived from the senior, single subject, individual Olympiads. For the EUSO to be accepted by EU science educators and governments, it had to mirror these Olympiads in some ways but be totally novel in others. It had to embody and reflect new ways of teaching and learning. It needed to add value to the science education experience of young students and their teachers.Each year, for one week at Easter time, sixteen year old student teams from across the EU gather and test their practical skills in biology, chemistry and physics. This book contains the tasks presented in the five Olympiads of the years 2003 to 2007. The interdisciplinary nature of the tasks makes them appealing for use in the science laboratories of the schools of today. The book will also serve as a valuable resource of interesting and challenging experiments for young scientists everywhere.