Experimental and pre-clinical life cell approaches traditionally use two-dimensional (2D) cell cultures, which are easy to establish, but frequently provide results of limited significance, since cells are lacking a physiological microenvironment. In contrast, three-dimensional (3D) cell cultures, e.g., multicellular tumor spheroids (MCTS), maintain tissue-like properties and therefore provide a more realistic background for experimental studies, e.g., screening of pharmaceutical agents 
. However, imaging of 3-dimensional specimens is challenging, since the sample thickness commonly exceeds the depth of focus of a conventional detection system, and light scattering considerably impairs the image quality. Therefore, methods based on optical sectioning, e.g., confocal laser scanning microscopy (CLSM) 
, Optical Sectioning Structured Illumination Microscopy (OS-SIM) 
, or light sheet fluorescence microscopy (LSFM) 
are applied preferentially. Here, images are recorded plane by plane, and resulting 3D plots are calculated offline. A problem for CLSM related methods as well as for OS-SIM is that for imaging each plane the whole sample has to be illuminated, so that upon recording of the whole specimen phototoxic damages are likely to occur 
. Furthermore, photobleaching may increase in the course of an experiment and falsify the experimental results. Altogether, 3D imaging creates a large number of data (“big data”), which have to be handled appropriately.