Among the light mesons, the \eta is very well suited for tests of the Standard Model (SM). Besides its negative parity and predominantly SU(3) octet structure, the \et\ has the quantum numbers of the vacuum, it is comparatively massive and it is long-lived since first-order strong, electromagnetic and weak decays are suppressed. Since the \eta meson is an eigenstate of both C and CP, these fundamental symmetries can be studied in detail. Searches for C or CP violating decays such as \eta \rightarrow\gamma\gamma\gamma, \eta \rightarrow\pi\pi, \eta \rightarrow\pi⁰ e⁺e^- and for effects beyond the Standard Model in \eta \rightarrow\pi⁰ e⁺e^-are challenging research topics. New experimental facilities that will come into operation in the next few years will allow detailed investigations of the \eta rare decays. In Uppsala, a wide-angle spectrometer, WASA, is being prepared for investigations of symmetries, searches for exotics and for precise measurements of decays which are sensitive tests of Chiral Perturbation Theory, for example the decays \eta \rightarrow 3\pi and \eta \rightarrow\pi⁰ \gamma\gamma.

PACS numbers: 11.30.Er, 13.20.Jf, 13.25.Jx, 13.40.Hq