If the DNA from a single cell was taken out and stretched end to end, it would span 2 meters. But all that DNA has to fold up tightly inside a single nucleus only a few microns wide. Studying the patterns and rules of DNA folding, and the implications this folding has for disease or epigenetics is the field of 3D genomics.
Hi-C data represent one major approach for studying 3D interactions within the cell, using a technique known as contact mapping. See more below from Dr. Erez Aiden's talk at the Scripps Research Translational Institute.