The 1926 Nobel Prize in Physics was awarded to Jean Baptiste Perrin for his work on the discontinuous structure of matter and the discovery of sedimentation equilibrium. This recognition marked a milestone in the acceptance of atomic theory, providing robust experimental confirmation of the existence of atoms and molecules through the study of Brownian motion.

Perrin, building on the theoretical predictions of Albert Einstein and Marian Smoluchowski, conducted a series of meticulous experiments. He observed pollen particles suspended in water, demonstrating that their random and erratic movement, Brownian motion, was a direct consequence of impacts from invisible water molecules. His precise measurements of particle distribution as a function of height, known as sedimentation equilibrium, allowed him to determine Avogadro's number with unprecedented accuracy. This value, which relates the macroscopic to the microscopic scale, was crucial for establishing the reality of atoms.

Prior to Perrin's work, the existence of atoms was a widely debated hypothesis within the scientific community. Although atomic theory had been proposed much earlier, it lacked conclusive experimental proof to convince everyone. Perrin's experiments not only validated Einstein's equations for Brownian motion but also provided irrefutable evidence of the discrete nature of matter, settling the debate and laying the groundwork for much of modern physics and chemistry.