Here's why:

* DNA is the blueprint of life: It contains the genetic instructions for building and maintaining an organism.

* Cells need instructions: Every cell needs to know how to function, grow, and divide.

* Exceptions: There are a few exceptions to this rule, such as red blood cells (erythrocytes) in mammals, which lose their nucleus and therefore their DNA during maturation.

Therefore, the vast majority of cells in your body, from skin cells to brain cells to muscle cells, all contain DNA.