The document is about deoxyribonucleic acid (DNA), the nucleic acid that contains the genetic instructions for all living organisms. It describes DNA as having a double helix shape and being composed of nitrogenous bases, deoxyribose sugar, and phosphate molecules bonded together in pairs. The bases are adenine, cytosine, guanine, and thymine, which bond together in specific base pairs to form the sides of the DNA helix structure.