Chromatin beads. Computer artwork of strands of DNA (deoxyribonucleic acid, pink) coiled around histone cores (blue) to form the less condensed ('beads on a string') form of chromatin. At upper left, a close-up of the pink tubes representing the DNA strand shows the double helix structure. DNA, the molecule that carries the genetic code that forms the basis of all life on Earth, is found in cell nuclei. It is a long molecule and has to be tightly coiled to fit inside the nucleus. Each set of two DNA loops around a histone core is known as a nucleosome. Further compacting and packaging (not seen here) form the denser forms of chromatin, and eventually the cell's chromosomes.