While there are many different types of imaging technologies, all rely on adequate contrast in order to distinguish components of interest. As such, contrast agents or media are used to enhance the quality of medical images. The lanthanide series consisting of 15 metallic chemical elements has proved valuable to medical imaging due to the luminescent properties of its members. European researchers working on the project ‘A combined approach to smart imaging agents- using heterometallic lanthanide complexes as diagnostics’ (MRLI) sought to develop new contrast agents for use in multimodal imaging. Multimodal imaging enables the integration of anatomical, functional and molecular information obtained from various imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). While much attention has been given to the interesting features of interactions between two or more metallic centres, most work has focused on compounds of the same metal (homobimetallic compounds). Linking lanthanide complexes with other groups to produce heterometallic lanthanide complexes offers greater potential for tailoring effects. Investigators focused on the synthesis of new families of lanthanide complexes via linking reactions. Successful bioconjugation was achieved via co-called Ugi reactions and the use of simple ‘click chemistry’ reactions that lead specifically to one product. In order to target the contrast agents to specific substrates, researchers linked the complexes to peptides, bioactive sugars and photoactivated molecules. Further investigations elucidated mechanisms for modulating the behaviour of the new class of multimodal imaging agents to produce ‘switchable’ contrast media whose properties are altered by electrical and chemical changes in the local environment. Other project work focused on the development of cell-targeted imaging agents that target cell membrane surfaces and cellular DNA. MRLI contrast agents should have wide application in the booming medical imaging market with important implications for EU citizens and their health.