This chapter provides a brief overview of molecular imaging techniques and its present and future potential in personalized medicine (PM), with special a focus on the magnetic resonance imaging (MRI) approach. It discusses the techniques that allow for the in vivo visualization of molecular processes at the nanoscale resolution (nano-MRI). The chapter highlights the potential of nano-MRI in the improvement of MRI sensitivity and consequently on the impact of this widely used technique for diagnosis and personalized treatment. Early diagnosis and treatments tailored precisely to an individual patient are the primary goals of PM, conceived as a system for delivery of the necessary treatment with the best timing for a specific patient. Diamond impurities on the atomic scale have been used as spin sensors to obtain remarkable results in nano-MRI, by exploiting interactions between magnetic dipoles in place of detection by induction means.