Cell structure. Fluorescent light micrograph of a cultured cell from a cell line derived from African green monkey kidney cells. The nucleus, which contains the cell's DNA (deoxyribonucleic acid), is blue. Microtubules, part of the cell's cytoskeleton, are red. The cytoskeleton is responsible for intracellular transport, structure and motility of the cell, as well as segregating the chromosomes during nuclear division.