Recent advances in molecular biology have unmasked the complexity of many cancers that we previously grouped together when determining diagnostic and therapeutic paradigms. Whereas treatment was previously determined primarily by the extent of disease as defined by anatomical imaging, modern oncology practice is moving inexorably towards personalised medicine wherein cancers will be managed by highly specific and targeted approaches based biological characteristics driven by the genomic landscape of individual cancers. Generally, these factors are determined from biopsy, which, due to limited sampling, don’t necessarily capture the heterogeneity that can exist within individual tumours and between lesions in a given patient. While able to define the presence and extent of disease within the conventional framework of disease staging, and generally to do so more accurately than conventional imaging, molecular imaging can also characterise the heterogeneity that exists in many disease processes at a biological level. This allows personalised selection of treatments and earlier assessment of response. Moving from “lumpology” to whole-body characterisation of “molecular biology” will provide unique insights into cancer treatment. PET, in particular, provides a powerful translational platform for preclinical drug development and increasingly, as novel tracers become available, will transform clinical imaging.