Identification of nucleoli based on the distribution of both DAPI and Pol II. (a) Original confocal images of HeLa cells that transiently synthesize a GFP-tagged protein. Cells are co-stained with DAPI (blue) and antibodies against Pol II (red). (b) The Add function is applied to DAPI and Pol II images to better demarcate nucleoli. Nucleoli are detected with the Detect dark holes and Median filters. (c) Segmentation and overlay of segments with the DAPI, Pol II and statistical correction images.