 Topological K-theory was discovered by Atiyah and Friedrich Hirzebruch who were inspired by Grothendieck's proof of the Grothendieck–Riemann–Roch theorem and Bott's work on the periodicity theorem.This paper only discussed the zeroth K-group; they shortly after extended it to K-groups of all degrees, giving the first (nontrivial) example of a generalized cohomology theory.Several results showed that the newly introduced K-theory was in some ways more powerful than ordinary cohomology theory.