To prepare and stain cells for examination with a light microscope.
A small square or circle of thin glass called a coverslip is placed over the specimen. It prevents the slide from drying out when it's being examined. Iodine stain can be used to stain plant cells to make the internal structures more visible.
Most cells are colourless. Stains are used to add contrast. Certain stains are also used to stain specific cell structures or cell products.
With cheek cells the stain methylene blue can be used. This stains the nucleus blue.