Stains are used in microscopy to help view bacteria, which are normally colorless and hard to see in their natural state even with a microscope. Methylene blue is a popular stain used to view microscopic life in brilliant color. It's attraction to acid makes it particularly useful for viewing animal cells since cell nuclei contain deoxyribonucleic acid (DNA).
For best results, follow the sequence below:
Prepare a wet mount slide with a specimen
Place a single drop of stain on one outer edge of the cover slip on top of your slide
Place some paper towel against the opposite edge of the cover slip - as close to the edge as possible
The paper towel will draw the stain underneath the cover slip
Wait until all of the stain has been pulled in between the cover slip and the slide
The stain should completely cover the specimen on the slide
If it does not, add another drop of stain to the edge of the cover slip
Remove the piece of paper towel and place the slide on the microscope stage and you should see cell nuclei show up as the darkest blue portion of the imagery.