DNA

Your genetic makeup (who you are genetically which controls things like eye color, hair color, bone structure, organ size, etc.) is controlled by the paring of the chromosomes contained from the female's egg (23 chromosomes from her) and the chromosomes from the male's sperm (23 from him too) (you know how those chromosomes come together, right??). Each of the 46 total chromosomes is made up of long threads of a very specific type of molecule called DNA, or deoxyrivonucleic acid. It goes one step further - each molecule of DNA is made up of thousands of genes, which determine your "genetic makeup". So you see, DNA is really the carrier of the genetic material that determines who you are (genetically).