Here's why:

* DNA (Deoxyribonucleic Acid): DNA is the molecule that contains the genetic instructions for building and maintaining an organism. It's like a blueprint that tells the cells what proteins to make and how to function.

* Genes: Specific segments of DNA are called genes, and each gene carries the instructions for a particular trait, like eye color or hair color.

* Chromosomes: DNA is organized into structures called chromosomes. Humans have 23 pairs of chromosomes, one set from each parent.

So, DNA is the fundamental molecule that holds the hereditary information passed down from one generation to the next.