Two chains of the diatom Chaetoceros socialis curve toward each other. Long spines come from each cell's four corners and intertwine to attach it to its neighbor cells' spines. One spine at each end of a cell is longer than the other, and these intertwine with the long spines of other cells, forming three-dimensional ball-like clusters of chains—hence the name 'socialis', for this 'social' behavior.