How To View Cells Under A Microscope?

All living organisms are made up of cells. Cells are the smallest part of a living organism and are around 0.01 mm - 0.03 mm long. To look at a cell close up, a microscope needs to be used. A typical animal cell is 10–20 μm in diameter, which is about one-fifth the size of the smallest particle visible to the naked eye.

Equipment You Will Need

• A microscope
• An onion (for plant cells)
• A slide and cover slip
• A cotton bud
• Some food colouring (blue or green works best)
• Disinfectant solution
• A plastic bag to dispose of the cotton bud

Observing Plant Cells: Onion Epidermis

1. Carefully cut an onion in half (or ask an adult). Peel a thin layer of onion (the epidermis) off the cut onion.
2. Place the layer of onion epidermis carefully on the glass slide, and cover with a cover slip.
3. Stain the layer of onion with food colouring so you can see the cells.
4. Place the slide onto the microscope stage and bring into focus.

Check out that strong cell wall structure. It is solid so that it keeps a plant's shape and structure.

Observing Animal Cells: Cheek Cells

1. Grab a fresh slide and pop a drop of food colouring on it.
2. Rub the tip of a new, clean soft-ended cotton bud against the inside of your cheek.
3. Transfer the cheek cells to the slide by rubbing the swab all over it.
4. Dip the cotton bud in the disinfectant solution, and dispose in a sealed plastic bag in the bin.
5. Stain the slide by rubbing it with a cotton bud dipped in food colouring, then rub the cotton tip with your cheek cells on it against the food colouring.
6. Drop the cover slip on the slide and place it on the microscope.

Unlike the plant cells, animal cells are soft and fleshy. Animals don't need cells to keep their structure — that's what skeletons are for.

How to Use a Compound Microscope

1. Move the stage (the flat ledge the slide sits on) down to its lowest position.
2. Place the glass slide onto the stage. Be careful pushing it under the clips that the cover slide doesn't move or crack.
3. Select the lowest power objective lens.
4. Turn the coarse focus knob slowly until you are able to see the cells.
5. Turn the fine focus knob slowly until the cells are in focus and you can see them clearly.
6. Repeat steps 1–5 using the higher power magnification to see the cells in more detail.

Calculating Magnification

To see an object, the eyepiece lens and the objective lens magnification are multiplied together to give the total magnification.

Total magnification formula

Total magnification = eyepiece lens magnification × objective lens magnification. For example: 10 × 20 = 200, so magnification = 200.

Standard magnification levels

Most educational-quality microscopes have a 10x eyepiece and three objectives of 4x, 10x, and 40x, providing magnification levels of 40x, 100x, and 400x. At least 400x is needed for studying cells and cell structure.

Field of view at different magnifications

At 40x magnification you will be able to see 5mm. At 100x magnification you will be able to see 2mm. At 400x magnification you will be able to see 0.45mm, or 450 microns. At 1000x magnification you will be able to see 0.180mm, or 180 microns.

What You Can See at Different Magnifications

When using a high power microscope (also known as a compound microscope) it is best to start out with the lowest magnification, get your specimen in focus, and then move up to the higher magnifications one at a time. This is the easiest way to ensure that you will be able to focus in on your object quickly. At 400x magnification you will be able to see bacteria, blood cells, and protozoans swimming around. At 1000x magnification you will be able to see these same items, but you will be able to see them even closer up.

Microscope Types and Optical Considerations

• The light microscope can resolve details 0.2 μm apart.
• Living cells are seen clearly in a phase-contrast or a differential-interference-contrast microscope.
• Images can be enhanced and analyzed by electronic techniques.
• Tissues are usually fixed and sectioned for microscopy.
• Different components of the cell can be selectively stained.
• Specific molecules can be located in cells by fluorescence microscopy.
• The confocal microscope produces optical sections by excluding out-of-focus light.
• The electron microscope resolves the fine structure of the cell.

The objective lens, which is part of the set closest to the slide stage, produces an enlarged, inverted (upside-down) image of the specimen. The eyepiece lens then magnifies the image further. It is important to get as high quality optics as you can afford, even for a beginner, so they don't get frustrated by constantly blurry views through their microscope. Quality glass optics are recommended; plastic optics, like those on most toy microscopes, produce blurry images.

Choosing the Right Magnification for Cell Viewing

400x magnification

400x is ideal for high school biology. At this level you will be able to see bacteria, blood cells, and protozoans. Cheek cells are pretty clear at 40x, 100x, and 250x as well.

1000x magnification

1000x is best for college microbiology. You'll be able to see greater specimen detail with a 1000x microscope (10x eyepiece lens with 100x objective lens), but generally it's only essential if you're doing a microbiology course or using it in a laboratory. Note: while the 1000x magnification level provides greater detail, it takes more time and care to use — you'll need to apply immersion oil to the slide and clean the oil off the slide and microscope objective after each use. You'll also need to use more care in adjusting the contrast and focus.

Eukaryotic vs prokaryotic cells

Eukaryotic cells will be significantly larger than prokaryotic cells. However, without staining, only nuclei and chloroplasts will likely be discernible under a light microscope.

Staining and Specimen Preparation

Light microscopes possess low magnification and resolution, but can view living specimens in their natural colours. Microscopy depends as much on techniques for preparing the specimen as on the performance of the microscope itself. Food colouring is used to stain cell samples so you can see them under the microscope. For more advanced cell work, if you want to look at bacteria you'll have to order a gram stain kit. If you want to look at immune cells you'll probably have to use a blood stain using Diff-Quik, or you can spit onto a slide and see epithelial cells without doing any kind of stain. Pond water also does not require a stain and is a good starting point for viewing living microorganisms. Ciliates and most living microbes can be found in houseplant soil as well as pond water, while tardigrades can be found in moss.