Einstein didn't make any direct discoveries about the atom's structure or internal workings. He focused on the behavior of light and its interaction with matter, which led to some important insights that have applications in understanding atoms:

* Photoelectric effect: In 1905, Einstein explained the photoelectric effect by proposing that light is quantized, meaning it exists in discrete packets of energy called photons. This idea revolutionized our understanding of light and paved the way for quantum mechanics. While not directly about atoms, it impacted our understanding of how light interacts with them.

* Brownian motion: In 1905, Einstein also explained Brownian motion, the random movement of particles suspended in a fluid. This theory provided strong evidence for the existence of atoms, which had been debated for centuries. It helped solidify the idea that matter is made up of discrete particles.

While Einstein didn't directly "discover" anything about the structure of the atom, his work on light and Brownian motion greatly impacted our understanding of the atom's behavior and existence.

It's worth noting that Niels Bohr later applied Einstein's theory of quantized energy to develop a model of the atom, explaining how electrons orbit the nucleus.

So, while Einstein's contributions weren't about the atom's internal structure, they played a vital role in shaping our modern understanding of the atom and its interactions with light.