Surely somewhere somehow in your life you've used a microscope. If this was in grade school, perhaps the teacher set it up for you, but most do not escape high school or college, even as non-science types, without using one at some point. Here is your basic microscope you might encounter in a biology or forensic chemistry lab or such.
The light shines up from the bottom, through your sample, up through the objective lens that magnifies the image and through the eye tube to your eye. The eyepiece usually adds additional magnification (10X). A choice of three objective lenses that can be "dialed in" is quite common. Note the different lengths of these. The shortest lens is the lowest magnification lens and is often called the low power objective. As lens length increases so does the magnifying power of the lens. The technique for using the microscope is pretty universal and begins with something that sounds rather silly: Finding your sample when you look through your microscope! If there's dust on the lens or the stage, etc., depending on what you're looking for, you might find yourself looking at something other than your sample. Dumb as that sounds, it's far more common than you might think, especially if what you're looking at is a hair or a fiber to begin with! The focus knobs work to adjust the vertical height between the sample and the objective lens -- this is called the working distance -- within the range of heights you see your sample, outside that range you basically see nothing. The working distance is the longest for the low power objective and can be very small indeed for the higher power objective (which, incidentally, tends to be the most expensive and delicate of the objectives)
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