  We give a brief review of superconductivity at ambient pressure in elements,
alloys, and simple three-dimensional compounds. Historically these were the
first superconducting materials studied, and based on the experimental
knowledge gained from them the BCS theory of superconductivity was developed in
1957. Extended to include the effect of phonon retardation, the theory is
believed to describe the subset of superconducting materials known as
`conventional superconductors', where superconductivity is caused by the
electron-phonon interaction. These include the elements, alloys and simple
compounds discussed in this article and several other classes of materials
discussed in other articles in this Special Issue.
