Imaging mass spectrometry (MS) allows a remarkable range of measurements including diagnosis of disease state of tissue based on detailed information on its chemical constituents, especially lipids and proteins. The recent emergence of ambient ionization allows imaging in the open environment without sample preparation. In this review, we briefly describe the history of imaging MS highlighting its main techniques and applications. We also demonstrate how the detailed molecular information obtained by imaging MS makes this technique suitable for a range of forensic and clinical applications with the potential to be successfully developed all the way to intra-surgical practice.