Microscopes that use light to magnify objects effectively reached their limit by the mid-19th century. The invention of the cathode ray tube gave scientists such as Heinrich Hertz the idea that a CRT could possibly be used to concentrate electrons like a microscope concentrates light. It was not until 1931 that Ernst Ruska and Maximillion Knoll would successfully prove this theory to be true.
An electron microscope is not something that the average person can afford. A typical seller such as TechnicalSalesSolutions offers electron microscopes that cost anywhere from $85,000 to close to $1 million. They also require expensive cooling systems and extremely high (and thus costly) amounts of energy.
Not just any scientist can properly use an electron microscope; it requires separate training just for its' operation. In order to view an object using electrons, you must create a vacuum to prevent air from diffusing the electrons. The samples themselves also need careful preparation to survive the scanning process, which takes much longer than preparing a sample for a light microscope.
It is almost impossible to observe a material drying in the vacuum environment of a normal scanning electron microscope, which applies to most samples from organic matter. These samples must be dried before being observed in a SEM. Some materials that are not quite a solid or a liquid, such as grease, cannot be observed in a SEM at all. These require a different type of electron microscope called an environment SEM.
The electron microscope is used in a variety of scientific fields from medicine to semiconductors. IBM uses this type of microscope to identify mistakes in computer chips as small as a few atoms. In medicine, the electron microscope can look at the structure of viruses and DNA. They are often used in biopsies to make assumptions on whether or not a person has cancer.