Many essential processes in biology share a common fundamental step—establishing
physical contact between distant segments of DNA. How fast this step is accomplished sets
the “speed limit” for the larger-scale processes it enables, whether the process is antibody
production by the immune system or tissue differentiation in a developing embryo. This
naturally leads us to ask, How long does it take for DNA segments that are strung out over
millions of base pairs along the chromatin fiber to find each other in the crowded cell? This …