Of all the microscopes that are available, the original design is still used today in some cases. This type of microscope is called an optical microscope or a simple optical microscope. These use a single ocular lens opposed to the series of lenses in all other microscopes. Simple microscopes were the first ones made and fathered the science of microscopy, or the study of samples through a microscope.

Production of simple microscopes started with a Dutch spectacle maker named Hans Janssen around the late 1500's. Janssen's young son, Zacharias, was born around 1590. He acquired his father's love for the microscope and took over the production process. Although we know that both contributed to the development of the microscope, their work was not well documented so the extent of their innovation comes into question.

The invention of the compound microscope is said to be creditable to Zacharias Janssen, but that is based on a statement from Zacharias himself late in the 17th century and so is in question.

Building upon the Janssen's theory, Robert Hooke started to improve upon the simple microscope. Based on his findings and work, he published a book, Micrographia, in 1665, which featured observations both microscopic and telescopic as well as a number of original biological theories. Here is where Hooke coined the phrase “cell” in reference to his microscopy studies. This term refers to the similarity of what Hooke saw to a monk's room, called a cell.

In the preface of that book were instructions to build a microscope. Those plans or instructions were adopted by Anton Von Leeuwenhoek to further the science of microbiology. Leeuwenhoek is renowned as the father of microbiology to this day.

All of this was done using simple optical microscopes. Leeuwenhoek is credited with producing only simple microscopes, but they were the best ones made at that time.

The original idea came from the magnified images viewed through a bowl of water. These images were blurry and distorted, as you can imagine, so improvement was imminent. Although simple, this idea propelled microscopy down through the years to what it has become today. A clearer, sharper image was sought. This led to the development of the simple optical microscope and, later, contributed to the invention of the compound microscope.

Simple microscopes operate on the same principles as all light microscopes using light absorption and magnification properties. There is a light source under a sample, which is held to a platform under a lens. This lens is a concave (arched) lens and offers a larger view of what is under it. The level of magnification can reach 266X in this manner, depending on the power of the eyepiece.

They also have the same parts as other optical microscopes. The major parts are the eyepiece, body, lenses, nosepiece, stage and light source. There are usually two knobs for adjustment on the side of the scope called fine adjustment and coarse adjustment. The coarse adjustment will move either the stage or the upper parts of the scope to bring the sample into focus while the fine adjustment will sharpen the image after the coarse one is adjusted.