DNA is located inside the nucleus of cells. It contains the genetic instructions for living organisms. To extract DNA at home, one rinses their mouth with saline to collect saliva and cheek cells containing DNA. This is spit into a mixture of water and detergent, which is agitated to break open the cells and release the DNA. Cold alcohol is added, causing the DNA to separate and appear as a white substance at the top, while other compounds dissolve. The extracted "goo" is one's unique DNA.