I've been reading this paper entitled "A high-resolution map of the three-dimensional chromatin interactome in human cells", about interactome in 3D chromatin.
We next applied the above algorithm to the 518,032 anchor regions in the human genome, with each containing one or a few HindIII restriction fragments (fragments shorter than 2 kilobases (kb) are merged) (Fig. 2a), and uncovered a total of 1,116,312 chromatin interactions with a false discovery rate (FDR) of 0.1
Simple questions: what are these anchor regions in the human genome?
How could I group them into types/categories?