The solar microscope is, in fact, a projector. Using sunlight, you can magnify images on a wall or screen. In a time when electric light did not yet exist and bright light sources such as the spotlight and incandescent lamp had not yet been invented, sunlight was really the only light that could sufficiently illuminate preparations. To catch sunlight, the mirror was mounted on the windowsill or over an opening. The mirror reflected sunlight, passed through the body of the microscope and projected the preparation on the wall. It should be used in totally dark rooms. The solar microscope was invented in the 17th century and was used frequently until the middle of the 19th century, especially in schools and universities.