Einstein published four papers in 1905. Each of these four papers is enough to win the Nobel Prize. These achievements have had a far-reaching impact on the whole world, and Einstein is famous for it. Einstein explained the photoelectric effect through quantum theory in his first paper "Inspirational Views on the Generation and Transformation of Light", and finally proved the existence of energy photons and photons (that is, particles of light).

The other is Brownian motion, and the other is about the determination of atomic size. From these results, we can see that Einstein accounted for half of the two most important academic contributions to physics in the 20th century. In addition to the theory of relativity, quantum mechanics and photoelectric effect all started from Einstein.

In the paper published that year, Einstein was convinced that atoms did exist. Before that, for the scientific community, the atom was more a useful mathematical tool for equations than a physical entity. Suppose that hot water is composed of many unstable water molecules. Water is hot, and these molecules are unstable, moving around and hitting pollen irregularly. Einstein deduced that the movement of pollen was the result of collision. Einstein's biggest problem is that he needs to combine thermodynamics and classical mechanics to explain his point of view. The latter describes the motion of objects, while the former studies large-scale systems.