As part of an NIH consortium I work with two teams that are collecting multi-scale anatomical data on the human vagus nerve with one of the objectives being to start to get a handle on the variability between individuals. The variability that the experimental teams are seeing is beyond anything I expected, though admittedly my assumptions were naive. The branching structure and routing of the nerves is basically unique per human and we are in the processes of determining whether there are invariant rules (e.g. for branch ordering) that apply across all individuals. And that is at the level of gross anatomy. So we aren't even done with gross anatomy, despite many biologists thinking that the foundations are complete and have been since the 16th century. Turns out that if you want to be able to apply our knowledge of gross anatomy for more complex clinical use cases we need significantly more data about basic variability in structure so that we know what additional data we need to collect for each individual.