Gregor Mendel is famous for his works and experiments with the garden pea. His findings changed the outlook of biology as the world knew it. But even before Mendel was curious about inheritance, a British farmer did his own experiment with a type of garden pea in the 1790's. When Mendel decided to repeated this experiment he did something entirely new, he counted the number of different pea plants resulting from each cross. Mendel most likely chose to use the pea plant because they are easy to cultivate, small in size and reproduce quickly with a large amount of offspring. Pea plants are also able to reproduce in two ways: self-fertilize and cross-fertilize. Self-fertilization is when the sperm of the flower fertilizes the egg of the same flower. In contrast cross-fertilization occurs when pollen is exchanged by hand from one flower to another. There are many different varieties of the garden pea which was an added advantage to Mendel.

Mendel chose seven traits to study: flower color, seed color, seed shape, pod color, pod shape, position of the flower on the stem and height of the plant. Every one of the tested traits had contrasting forms: plant height could be tall or short; flower color white or purple.

The experiment can be broken into three steps of description. First Mendel let the different pea plants self-fertilize for generations. This ensured that the plants to be studied were of a true or pure breed, meaning their offspring would only produce one form of each trait. Mendel named this generation the parental, or P, generation for their pure breed existence. Therefore white flowered plants would only produce white flowered offspring. Second, he cross-fertilized the two contrasting parental generations. He placed the pollen from the white flowers and placed it in the purple plant. He then collected and grew the resulting seeds, which he named the F1 generation. Mendel observed that all the offspring had purple flowers and that none were white. Next he allowed the F1 generation to self-fertilize and grew seeds from those plants and called the offspring the F2 generation. This time around there were white and purple flowered plants. For every white flowered plant there was about 3 purple flowered. Mendel observed the same ratio of 3:1 in every trait he crossed. After studying all of his results, Mendel made up rules summarizing his ideas of inheritance.