Gregor Mendel, a priest was very curious about how traits were passed from one generation to another. He experimented with peas (29,000 plants!) for seven years and used mathematical principles to figure it all out.
Mendel determined that traits aren't blended but are instead passed on, intact, from parent to child. He found that everyone got two genes for each trait — one from the mom and one from the dad.
He also concluded that some traits are dominant and some are recessive.
Mendel took a tall pea plant and crossed it with a short one. He expected medium pea plants, but what he got was all tall pea plants! Mendel then crossed these tall babies (he called them the F1 generation) and he got three tall plants and one short plant.