Fluorescent proteins provide an incredibly powerful avenue for exploring biological function at the molecular scale in living systems. However, light does not penetrate opaque tissues, which hinders the use of fluorescent probes in complex in vivo environments like the animal brain and deep-seated tissue infections. Our group approaches this challenge by pursuing the development of molecular MRI reporters to image biological targets located at any arbitrary depth inside live animals of all sizes. To accomplish this goal, we draw on an assortment of techniques involving protein engineering, genetic editing, viral gene delivery, mammalian cell and bacteriophage engineering, and live animal preparations to create MRI probes for applications in cancer biology, neuroscience, and microbial imaging. In this talk, I will highlight our latest efforts in developing biomolecular tools for imaging living systems in unconventional ways: for example by modulating water movement in and out of cells, converting antimicrobial immunity proteins into calcium biosensors, and co-opting radioprotective peptides for in vivo bacterial imaging.