Biology is the only known phenomenon which uses molecular nanotechnology – the manipulation of matter locally and deliberately on the atomic or molecular scale. It follows then that biological conditions and diseases must originate from alterations in these nanoscale processes. Mutated genes, misfolded proteins and infections caused by nanoscale viruses and pathogens can lead to cell malfunction or miscommunication, eventually leading to life-threatening diseases. The nascent field of nanomedicine has attempted to treat these systems by interacting with them at their native scale using engineered materials and systems with features in the nanoscale range (0.1-100 nm). In this Review, we highlight the uses of nanomedicine in the diagnosis, treatment and prevention of disease, as well elucidate a common mechanism of action used by many nanomedicine technologies. The incredibly high surface to volume ratio of nanoscale materials allows multivalent presentation of biologically functional molecules. This leads to high local concentration and the enhanced rates of reaction essential for biological processes. Here we show that optimizing this enhancement effect using fundamental principles of statistical mechanics is achievable. The application of this framework to engineering nanomedicine technologies is also presented.