Not stopping at the laws of classical physics, pioneers between late 19th and very early 20th century probed further. The results: X-rays by Wilhelm Roentgen, properties of electron by JJ Thomson, radioactivity by Marie and Pierre Curie, model of an atom by Ernest Rutherford, and the Michelson-Morley experiments.
These discoveries and studies, in turn, acted as the gateway to explore the natural phenomena at a microscopic (atomic) or sub-microscopic level.