Netwon's (et. al.) deterministic description of mechanics (cause and effect).
Maxwell's description of light as an electro-magnetic wave (1854-8).
Riemann's description of electro-magnetism as oscillations in 4-D (1856).

The above's 'unification' of the Electric and Magnetic Interactions.

Boltzman's description of black body radiation (?). br> Einstien's description of curved space-time (1905).

The Unification of Gravity and the Electro-Magnetic Interaction- Its contribution to modern cosmology.

Hubble's Law (1920s) - The universe is expanding
Big Bang Theory - There was a moment of creation in which the energy density was very high and the interactions were unified -- physics was simple!

Development of Quantum Mechanics (1900-1958) the probabilistic description of the interactions. (One cause, many possible effects)
Development of high-energy particle accelerators (1930-present) to probe high energy density regime (like that of the early universe)