Here's a breakdown:

* Ernst Ruska is recognized as the primary inventor of the electron microscope. In 1931, while working on his PhD at the Technical University of Berlin, he designed and built the first transmission electron microscope (TEM), capable of magnifying objects up to 400 times.

* Max Knoll, Ruska's supervisor, played a crucial role in the early development of the electron microscope. He contributed significantly to the design and construction of the first prototype.

While Knoll and Ruska were the first to develop a functioning electron microscope, other researchers made crucial contributions to its advancement. Notably, Reginald Rudenberg filed a patent for a similar device in 1931, although his design was not realized practically.

The invention of the electron microscope marked a significant breakthrough in microscopy, allowing scientists to visualize objects at a much higher resolution than previously possible with light microscopes. This paved the way for numerous advancements in various fields, including biology, medicine, and materials science.