OBJECTIVE: INTRODUCTION: PROPER USE OF MICROSCOPES: In this lab you will learn the basic skills needed to stain and mount wet slides. You will  also learn about magnification, resolution and the parts of the compound microscope.  The light microscope can extend our ability to see detail by 1000 times, so that we can  see objects as small as 0.1 micrometer (um) or 100 nanometers (nm) in diameter. The  transmission electron microscope extends this capability to objects as small as 0.5 nm in  diameter, 1/200,000th the size of objects that are visible to the naked eye. Without  microscopes, our understanding of the structures and functions of cells and tissues would be  severely limited. Revealing the structure of small objects, however, is not so much a function of the  microscope’s ability to magnify as of its ability to distinguish detail. Merely magnifying an  object, without increasing the amount of detail seen, is of little value to the observer. The ability  to distinguish detail is called  resolution  or  resolving power , and depends on the wavelength  of light used and on a value called the  numerical aperture (NA)  a characteristic of  microscopes that determines how much light enters the lens. In its simplest form, resolution can  be expressed by the formula: resolution = wavelength 2 X NA Under normal conditions, resolution is increased by decreasing the wavelength of the  light source; e.g., if you use a green filter that permits light with a wavelength of 500 nm to pass  through a microscope lens with a NA of 1, then the resolution is 500 nm / 2 x 1, or 250 nm. This means that you can see 2 objects that are at least 250 nm apart as 2 distinct objects;  objects closer together than 250 nm will appear fuzzy or as one object. If you use a blue light  (or a blue filter that provides light at a wavelength of 400 nm) and a lens having an NA of 1, the  resolution would be equal to 400 nm / 2 x 1, or 200 nm. The 2 objects observed under these  conditions could be 50 nm closer together than those seen with a green filter and still be seen  as 2 separate objects. Knowing the significance of the wavelength of light in the ability to distinguish detail, you  can appreciate the role of electron microscopes and microscopes that use ultraviolet light in  defining the structure and function relationships of cells and organelles (sub cellular structures). In todays lab you will be using the compound microscope. Despite their sturdy  appearance, all microscopes are delicate, precision instruments. They should be handled  carefully and with common sense. The following suggestions will help you avoid some  common mishaps. AN INTRODUCTION TO THE COMPOUND MICROSCOPE