COVER ILLUSTRATION Seeing the invisible ? Intraoperative Optical Imaging (IOI) is a technique that gives us unique insights on the human brain and it's function. The method uses subtle changes in the optical properties of the exposed cortical brain tissue to detect and visualize hemodynamic changes which are connected to specific brain functions. Since IOI needs beside an undisturbed view on the cortical surface only a camera system and light within the visible range it is well suited for application during neurosurgical interventions. In our paper ?Characterization of Cortical Hemodynamic Changes Following Sensory, Visual, and Speech Activation by Intraoperative Optical Imaging Utilizing Phase-Based Evaluation Methods? we used IOI to characterize the hemodynamic changes on the brain surface following different types of stimulation in patients that underwent brain tumor surgery. The graphics illustrates the several aspects of the methodology and the results of our paper. The three images in the middle are showing phase angle maps, overlaid to the white light image of the exposed brain surfaces. The different maps are representing the response towards visual (left), sensory (right), and speech activation (middle) as shown in the result section of the paper and supported by the text above the whole image composition. The grid in the front is a polar histogram, we used for quantitative analysis and visualization of the results. Overlaid to the grid is the colorbar that we used for the phase angle maps, shaped as vortex. The colors correspond with different phase angles of the polar histogram. To underline the fact that IOI can be used to visualize functional brain areas during neurosurgical interventions, we added in the back an abstract painting of a neurosurgeon, looking through the sterile draped surgical microscope. The light source references to the fact, that IOI is an optical technology and therefore based on light.