To participate in EUSO, students must be 16 years of age or younger on 31 December in the year before the competition. From each country two (or occasionally one) teams of three students are selected. The competition consists of three, hour long, trivia style sessions of questions, including practical tests requiring laboratory skills and theoretical knowledge. The areas of science covered are biology, chemistry and physics.
EUSO is the brainchild of Mr. Michael A. Cotter, Dublin, Ireland. He aimed to create a more practical-based general science competition for younger students than existing international science olympiads such as IBO, IChO and IPhO. The first competition was held in 2003 in Dublin, Ireland. Seven countries took part and the competition has since grown to include forty teams from twenty-one countries in Europe in 2009.