This article is devoted to the cohomology of extraspecial \(p\)-groups. The authors point out the following purposes of the article: to provide a coherent and simplified account of much of the work which has been done in this area; to explain the current state of knowledge; to demonstrate a few of the many techniques which can be used in the field. Occasionally repeating a known argument from the literature, the authors usually present improved or different versions of most proofs. In conclusion they prove a general result which in many ways sums up a lot of the philosophy of this work. Theorem 14.1: If \(1\to N\to G\to \overline{G}\to 1\) is a central extension with \(N\) cyclic of order \(p\), then the subvariety of the kernel of the inflation map in the maximal ideal spectrum of \(H^* (\overline{G},K)\) is the same as the subvariety of the ideal generated by the extension class in degree two and all of its images under all Steenrod operations.