With few exceptions, each of us has about 3 billion bases in our DNA on 46 chromosomes (and 2 sex chromosomes). If you stretched out that DNA, it would be 2m long! How can something so long it fit into cells which need a microscope to be seen?
Your cells package the DNA, allowing it to access the pieces that it needs to read the instructions needs. The rest is compressed by creating coils upon coils.
The most intense compression occurs when a cell is ready to divide. At this time, it is compressed into a familiar shape that we call a CHROMOSOME. This chromosome is one molecule of DNA, compressed into a small bar. Cells make a copy of every base before dividing. When the cell makes a copy of the DNA, it forms an X shape, connected at the middle by a point called the CENTROMERE.
It’s this X shape that is the hallmark of a cell actively going through the motions of MITOSIS, or cell division.