The reactor-based laboratory at the Institut Laue-Langevin is recognized as the world's most productive and reliable source of slow neutrons for the study of low energy particle and nuclear physics. The book highlights the impact of about 600 very diverse publications about work performed in these fields during the past more than 30 years of reactor operation at this institute. On one hand neutrons are used as a tool to generate nuclei in excited states for studying their structure and decay, in particular fission. Uniquely sensitive experiments can tell us a great deal about the symmetry characteristics of nuclei and their fission properties. On the other hand, studies with slow neutrons as the object of investigation are complementary to studies at huge particle accelerators. Experiments carried out at the ILL contribute to elucidate basic questions about the building blocks of the Universe by analyzing very precisely subtle neutron properties.