Based on our proprietary protein design and computational technology for metalloproteins, we have developed a novel class of protein contrast agents (ProCAs) with significantly increased both r1 and r2 relaxivities and a ~100-fold improvement in vivo contrast capabilities and doubled accuracy. This platform technology enables us to develop both blood pool (non-targeted) contrast agents for soft tissues and biomarker targeted molecular imaging contrast agents that address major unmet medical needs in non-invasive precision diagnostics. Due to optimized in vivo and relaxation properties, a single injection of the blood pool non-targeted ProCA contrast agents enables the acquisition of both bright contrast (T1-weighted) and dark contrast (T2-weighted) that has never been achieved before. For example, our contrast agents enable the early detection of small early stage tumors such as primary liver and micrometastatic lesions from breast, ovarian and uveal melanoma cancer down to 0.1-2 mm from the current threshold of 1-2 cm, at relatively late cancer stage. We have created a set of molecular imaging MRI contrast agents (tProCAs) that specifically target major biomarkers including EGFR, HER2/Neu, GRPR, chemokine receptor (CXCR4), PSMA, integrin, and collagen. These targeted MRI contrast agents have further improved sensitivity and specificity with the capability to detect infiltrative small lesions and distinguish benign and subtypes of cancers and their heterogeneity. These molecular imaging contrast agents have unique quantification capability for biomarker expression and occupancy with high spatial resolution due to their strong penetration capability in tumor tissue and the endothelial boundary. We have successfully applied these targeted MRI contrast agents to non-invasively access the expression levels and patterns of biomarkers for cancer staging and to monitor disease progression or regression upon treatment in cluster 2-3 D tumor cell clusters, infiltrative tumor patterns, and xenograft murine models for prostate cancer, lung cancer, breast cancer, ovarian cancer, pancreatic cancer, liver cancer and metastasis. For example, collagen targeted ProCAs are able to detect early stage liver fibrosis that is possible to be reversed with adequate treatment. Thus our molecular imaging contrast agents are expect to avoid limitations of the gold standard biopsy, including large sampling errors by non-invasive and quantitative MRI without use of radiation. Importantly, we recently demonstrated that protein contrast agents exhibit unprecedented metal selectivity over endogenous metal ions. The injected dose in mice application is also about 25-100 fold lower due to their optimized relaxivity, organ, tissue, and tumor distribution. We have not detected any acute toxicity and immunogenicity. These results clearly support the potential of ProCAs to mitigate metal toxicity associated with nephrogenic systematic fibrosis. Our protein-based MRI-CAs are expected to enable non-invasive disease early detection, staging, monitoring therapeutic effects, and image-guided treatment/ intervention with enhanced safety, sensitivity and accuracy in both clinical and preclinical applications.