Hierarchy structure of classified objects. Starting with a low threshold value, the whole embryo is segmented but cannot be classified as a valid object. When the threshold value increases, objects can be classified as valid and put in the hierarchy with the saved information. In the case of object separation, the associated object at the previous threshold, if any, is computed in order to put the objects in their right place in the hierarchy. The best object inside each branch is computed by maximizing the classification, and the segmented object is reconstructed.