Simplify the following text for a Grade 9 native English-speaking person.
Original: For example , each human cell has about 1.8 meters of DNA , but wound on the histones it has about 90 millimeters of chromatin , which , when duplicated and condensed during mitosis , result in about 120 micrometers of chromosomes .
Simplified: For example , each human cell has about 1.8 meters of DNA , but wound on the histones it has about 90 millimeters ( ? ) of chromatin , which , when duplicated and condensed during mitosis , result in about 120 micrometers of chromosomes .