When matter is reduced to nanoscale dimensions, unexpected properties emerge that are often completely different from those of the same materials at the micro- or macroscopic scale. Occupational exposure to manufactured nanomaterials (NM) affects workers in research laboratories, manufacturing plants, or sites where NM are used, the exact number of whom remains unknown to date. Furthermore, significant quantities of MNs are deployed annually in France across a wide variety of sectors, according to the national registry for mandatory annual reporting of substances in nanoparticulate form, R-Nano. At the same time, several experimental studies—though scattered, incomplete, and even contradictory—suggest harmful biological effects for certain families of MNs. Uncertainties therefore remain regarding the risks posed by certain NMs. Furthermore, metrological limitations persist in the assessment of exposures. Nevertheless, despite this context of uncertainty, occupational risk prevention for workers exposed to NMs is imperative, and existing regulations on occupational risk prevention remain applicable under the responsibility of employers. Occupational recommendations are made available to employers and occupational health services by the National Research and Safety Institute (INRS) and the High Council for Public Health (HCSP). In addition, health surveillance (the national EpiNano system) is essential for providing evidence-based data on the health risks to workers exposed to NMs. This manuscript, written by a multidisciplinary group, presents an overview of the state of the art regarding NMs.