  Until now no electric dipole moment of the neutron (nEDM) has been observed.
Why it is so vanishingly small, escaping detection for the last 65 years, is
not easy to explain. In general it is considered as one of the most sensitive
probes for the violation of the combined symmetry of charge and parity (CP). A
discovery could shed light on the poorly understood matter/antimatter asymmetry
of the Universe. The neutron EDM might one day help to distinguish different
sources of CP-violation in combination with measurements of paramagnetic
molecules, diamagnetic atoms and other nuclei. This review presents an overview
of the most important concepts in searches for an nEDM as well as a brief
overview of the worldwide efforts.
