Molecular imaging can be defined as imaging of biological processes in a living organism at the molecular and/or cellular level. To achieve this goal, genetic information and new chemistries have to be combined into new imaging probes detectable by sophisticated imaging techniques. In contradistinction to conventional imaging, which mostly detects architectural, or morphological distortions (a late event), molecular imaging should be able to detect molecular changes that are at the basis of diseases. The detection of subtle pathologic changes in early, asymptomatic disease should have a tremendous impact on healthcare as a whole.