Nettie’s research provided critical evidence for chromosomal theories of inheritance and expanded the fields of genetics, cytology, and embryology. Her scientific accomplishments are now inseparably incorporated into the big picture. She is known for illuminating the significance of the (Y) chromosome in sex determination. While others were pursuing the idea that sex determination was the result of environmental factors, Nettie was carefully watching mealworms. Which, she noted, produced two kind of sperm. Each type of sperm possessed a different chromosome, which fertilization would reveal, produced two different results in the sex of offspring. The truth was right in front of the eyes, but it took Nettie to see it, test it, and make it history - although the credit was often misplaced along the way.