Comparing segmentation results on the top and the side. Using a maximum projection, we show two portions of a three-dimensional image of an embryo fluorescently stained to label nuclei. (a) A projection along the optical axis, yielding a x-y image (the top of the embryo); (b) a projection perpendicular to that, yielding a x-z image (the side of the embryo). The nuclei on the top of the embryo appear well separated and distinct (a). Seen from the side, however, individual nuclei appear elongated along the z-axis due to limited axial resolution, which makes them more difficult to identify (b). The segmentation algorithm provided an accurate segmentation of nuclei (c) on the tops of embryo images, but (d) on the sides, a model was used to fine-tune the segmentation, resulting in a less accurate result.