Gregor Mendel discovered three principles of heredity: that the inheritance of each trait or "gene" is determined by the units that are passed down via descendants unchanged, that an individual will get one unit from each of their parents for each trait and that a trait may not show up in one individual yet it can still be passed on to a descendant. Mendel is known as the father of genetics, which is the study of understanding what happens in the transfer of genes from parents to children.
Mendel was a Central European monk who published his ideas on genetics in 1866, but did not receive recognition until 1900 after his death. He taught high school mathematics, Greek and physics in the Czech Republic, which was Brno at the time, as well as performing his own genetics research.
Mendel performed his research with plants when studying genetics. Since heredity is the same across species, Mendel's results were able to be applied to both animals and humans. Mendel performed his experiments on common garden pea plants because they were easy to grow in large numbers and he could manipulate their reproduction easily since the pea plants have both male and female reproductive organs.
Mendel was also able to breed pea plants so quickly that he was able to observe inheritance patterns in as many as two generations each year. Mendel observed the principle of segregation and independent assortment and his principles are considered to be "laws" by many scientists today.