Beginning in the 19th century, the field of genetics saw significant growth in thought. Though concepts of heredity were postulated long before the term entered the scientific lexicon, it wasn’t until Gregor Mendel’s work on pea plants in 1865 that the concept of heredity was fully understood. By 1944, Avery, MacLeod, and McCarty discovered that DNA was the “transforming principle,” the fundamental chemical component of genes (“1944: DNA Is \"Transforming Principle\,"” n.d.).