The successful development of nanomaterials illustrates the considerable interest in the development of new molecular probes for medical diagnosis and imaging. Substantial progress was made in the synthesis protocol and characterization of these materials, whereas toxicological issues are sometimes incomplete. Nanoparticle-based contrast agents (CAs) tend to become efficient tools for enhancing medical diagnostics and surgery for a wide range of imaging modalities. The multimodal nanoparticles (NPs) are much more efficient than the conventional molecular-scale CAs. They provide new abilities for in vivo detection and enhanced targeting efficiencies through longer circulation times, designed clearance pathways, and multiple binding capacities. Properly protected, they can safely be used for the fabrication of various functional systems with targeting properties, reduced toxicity, and proper removal from the body. This review mainly describes the advances in the development of mono- to multimodal NPs and their in vitro and in vivo relevant biomedical applications ranging from imaging and tracking to cancer treatment. Besides the specific applications for classical imaging (magnetic resonance imaging, positron emission tomography, computed tomography, ultrasound, and photoacoustic imaging), the less common imaging techniques such as terahertz molecular imaging (THMI) or ion beam analysis (IBA) are mentioned. The perspectives on the multimodal theranostic NPs and their potential for clinical advances are also mentioned.< Réduire