Chromosomes are the microscopic threadlike part of the cell that carries hereditary information in the form of genes. A defining feature of any chromosome is its compactness. For instance, the 46 chromosomes found in human cells have a combined length of 200 nm (1 nm = 10− 9 meter); if the chromosomes were to be unraveled, the genetic material they contain would measure roughly 2 meters (about 6.5 feet) in length.