That is the field of molecular biology and genetics and biochemistry
which has totally changed our perceptions of how life on Earth is
actually organized. Much of the biology to which you may have been
exposed until now has been a highly descriptive science. That is you
may have had courses in high school where you had to memorize the
names of different organisms, where you had to understand how
evolutionary phylogenies were organized, where you had to learn the
names of different organelles, and that biology was, for you, a field of
memorization.