In an unprecedented atlas, researchers begin to map how genes are turned on or off in different cells, a step toward better understanding the connections between genetics and disease.

Researchers at University of California San Diego have produced a single-cell chromatin atlas for the human genome. Chromatin is a complex of DNA

DNA, or deoxyribonucleic acid, is a molecule composed of two long strands of nucleotides that coil around each other to form a double helix. It is the hereditary material in humans and almost all other organisms that carries genetic instructions for development, functioning, growth, and reproduction. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).