The use of nanoparticles—small, virus-sized elements developed under laboratory conditions—is increasingly widespread in the world of biomedicine. This rapidly-evolving technology offers hope for many medical applications, whether for diagnosis or therapies. In oncology, for example, the growing body of research suggests that, thanks to nanoparticles, treatment will soon become more precise, more effective and less painful for the patients. However, the way nanoparticles interact with the immune system remained unclear and unpredictable until recently, restricting their potential medical use. Today, researchers from the universities of Geneva (UNIGE) and Fribourg (UNIFR), Switzerland, are close to solving the problem: they have devised a rapid screening method to select the most promising nanoparticles, thereby fast-tracking the development of future treatments. In less than a week, they are able to determine whether nanoparticles are compatible or not with the human body—an analysis that previously required several months of work. This discovery, which is described in the journal Nanoscale, may well lead to the swift, safe and less expensive development of nanotechnology applied to medicine.