Fluorescence imaging developments have also led to the development of hybrid fluorescence molecular tomography (FMT) X-ray CT (XCT) imaging (see Ale et. al., Nature Methods 2012 9(6), 615-620, 2012). These approaches are shifting the ways of detecting cellular and sub-cellular processes in animals and humans by virtually offering in vivo staining of important biomolecules that play a crucial role in disease progression or treatment. They can therefore lead to new exploratory, diagnostic and theranostic methods.