DNA is able to fit into a cell because of its shape. DNA is a double helix that can bend and twist in all sorts of directions. An easier example to visualize is a spaghetti noodle in a bowl. Stretched out straight, it wouldn’t fit in the bowl, but once coiled or twisted up, it would conform to the shape of sand bowl. Well, DNA can coil up just like a noodle can, which gives it the ability to become compact enough to fit into the nucleus of a cell. The way DNA molecules can all fit into the cell is because they coil around histone proteins, which once in a tight enough coil, become nucleosomes which can stack to then become chromatin. That is how about 6 feet of DNA can be squeezed into a microscopic cell.