This image shows the internal structure of a mouse pancreas, imaged with a SPIM microscope (Selective Plane Illumination Microscopy) like those that will be used at EMBL Barcelona. To track cells and molecules in a living tissue, specially-designed technology is needed. In the mid-1990s scientists designed non-invasive techniques like SPIM. Thanks to this method, researchers can record living tissues and organs in detail, by shining a thin sheet of light on them, one layer of cells at a time. SPIM enabled EMBL scientists to see a fish embryo’s beating heart for the first time.