Early editions of the first Olympiads were limited to the Eastern Bloc, but later they gradually spread to other countries.
[1] The Olympiads themselves are separate competitions each with its own organizing body, even though they are loosely grouped together as "ISOs".
The aims of each ISO are to promote a career in science; to challenge the brightest students from around the world; and to compare the various teaching systems of each country.
Although the competitions are aimed for secondary school pupils, the standards of the exams are extremely high.
[citation needed] Science Olympiads are international student competitions.