The Atomium was built as the main pavilion and icon of the 1958 World Expo of Brussels (Expo 58). In the 1950s, faith in scientific progress was great, and a structure depicting atoms was chosen to embody this. The Atomium's nine stainless steel clad spheres depict nine iron atoms in the shape of the body-centred cubic unit cell that could for example represent α-iron (ferrite) crystal, magnified 165 billion times.