The Pauli Exclusion Principle (PEP) is one of the basic principles of modern physics and, even if there are no compelling reasons to doubt its validity, it is still debated today because an intuitive, elementary explanation is still missing, and because of its unique stand among the basic symmetries of physics. We present an experimental test of the validity of the Pauli Exclusion Principle for electrons based on a straightforward idea put forward a few years ago by Ramberg and Snow (E. Ramberg and G. A. Snow 1990 Phys. Lett. B 238 438). We performed a very accurate search of X‐rays from the Pauli‐forbidden atomic transitions of electrons in the already filled 1S shells of copper atoms. Although the experiment has a very simple structure, it poses deep conceptual and interpretational problems. Here we describe the experimental method and recent experimental results interpreted as an upper limit for the probability to violate the Pauli Exclusion Principle. We also present future plans to upgrade the experimental apparatus.
