Nanotechnologies enable great opportunities for the development and use of innovative (nano)medicines. As is common for scientific and technical developments, recognized safety evaluation methods for regulatory purposes are lagging behind. The specific properties responsible for the desired functioning also hamper the safety evaluation of such products. Pharmacokinetics determination of the active pharmaceutical ingredient as well as the nanomaterial component is crucial. Due to their particulate nature, nanomedicines, similar to all nanomaterials, are primarily removed from the circulation by phagocytizing cells that are part of the immune system. Therefore, the immune system can be potentially a specific target for adverse effects of nanomedicines, and thus needs special attention during the safety evaluation. This DDTR special issue on the results of the REFINE project on a regulatory science framework for nanomedical products presents a highly valuable body of knowledge needed to address regulatory challenges and gaps in currently available testing methods for the safety evaluation of nanomedicines.