AbstractImaging without labeling has received increasing attention during the last few years as a minimally invasive modality to observe proteins, cells, and tissues, and to study biological specimens with minimized modification and sample preparation requirements. Within the last decade, quantitative phase imaging (QPI) has been continuously improved for the purposes of high‐resolution, label‐free quantitative microscopy [1]. QPI is minimally invasive. This means that samples under investigation are, for example, not influenced by fluorophores or dyes which can change physiological processes or affect the behavior of samples, like cellular motility or migration. Moreover, QPI requires only low light intensities for object illumination. Thus, potential harm from light to an investigated sample, which can cause, amongst other things, cell death or photo damage, is minimized. This is an essential precondition for the long‐term monitoring of biological samples such as living cell cultures in life sciences and biomedicine.