It's important to be well organized. And this is especially true for the genome—the entirety of an organism's genetic information, also known as DNA. The genomic DNA is several meters long but has to fit inside the cell's nucleus, which has a diameter of just around 5 micrometers. In mammals, the genome houses many thousands of genes and up to ten times more enhancers, which act like switches in gene activation. Sophisticated folding allows genes and enhancers to interact in an orderly manner. This is important because for an organism to develop properly and not fall ill, thousands of genes must be activated and read correctly at the right time. This is the only way that tissues and cells can form properly.