FMNsFunctionalized Magnetic Nanomaterials (FMNs) are mostly composed of a magnetic core, like iron oxide. They are functionalized with biocompatible coatings (polyethylene glycol, dextran, silica) and targeting molecules to optimize their performance in medical applications. FMNsFunctionalized Magnetic Nanomaterials (FMNs)’ properties, like super magnetism and high magnetic susceptibility, enhance the diagnosticDiagnostics detail and specificity, enabling more accurate disease diagnosis. The supermagnetic property of the FMNsFunctionalized Magnetic Nanomaterials (FMNs) provides strong magnetization in response to an external magnetic field, which improves the variation between tissues during MRI scans and at the same time functionalizationFunctionalization allows for the precise targeting of specific biological ligandsLigands (antibodiesAntibodies, peptidesPeptides, or small molecules), ensures high specificity in detecting abnormalities such as tumors, inflammation, or any vascular diseases. The design and synthesis of FMNsFunctionalized Magnetic Nanomaterials (FMNs) for imagingImaging applications depend on the particle size, shape, surface functionalisation, and biocompatibilityBiocompatibility, all of which influence their performance as contrast agents. For example, FMNsFunctionalized Magnetic Nanomaterials (FMNs) functionalized with ligandsLigands or antibodiesAntibodies can target certain specific cell receptors and provide molecular imagingImaging capabilities that go beyond conventional anatomical imagingImaging. FMNsFunctionalized Magnetic Nanomaterials (FMNs) are also expanding into multimodal imagingImaging systems, which combine magnetic propertiesMagnetic propertiesof FMNsFunctionalized Magnetic Nanomaterials (FMNs) with fluorescence for techniques like magnetic particle imagingImaging and positron emission tomography. These conjugated FMNsFunctionalized Magnetic Nanomaterials (FMNs) with fluorescent dyes facilitate real-time imagingImaging in preclinical studies, enabling simultaneous tracking and diagnosis. These advancements enhance the precision of diagnosticsDiagnostics and open new avenues for personalised medication. Surface functionalisation is the key to the versatility and effectiveness of FMNsFunctionalized Magnetic Nanomaterials (FMNs) in diagnosticDiagnosticsimagingImaging. This chapter reviews the use of FMNsFunctionalized Magnetic Nanomaterials (FMNs) as contrast agents in MRI and other imagingImaging modalities, explaining how their magnetic propertiesMagnetic properties enhance resolution and specificity in diagnosticDiagnostics procedures.