Illustration of 3D cell nuclei segmentation on a 2D slice. (a) A slice from 3D cell nuclei image. (b)Boundaries of small regions overlaid on the slice. The boundaries are obtained by the method in Section 2.2. (c) Edges of cell nuclei overlaid on the slice after the step of adaptive thresholding in Section 2.3. (d) Randomly color-coded extracted cells.