In 1911, Rutherford discovered that atoms not independent, they are controlled by something else, a nucleus. He noticed that the majority of an atom's mass is concentrated at a very tiny point in the center where the nucleus was located. The nucleus is a positive force surrounded by electrons which are negative free flying particles. Therefore, he also discovered that there is something smaller than an atom. In 1917, Ernest Rutherford "split the atom" discovering that atoms are made of more than one "part". This is important because we learned that we are able to split atoms to make different elements. "The Father of Physics" is a fitting name for Ernest Rutherford.
Here's a video of the "Gold Foil Experiment" which was one of his most widely known experiments.