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Key points

  • 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.
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Game - onion cells

Play an Atomic Labs activity to look at onion cells under a microscope.

You can also play the full game.

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Video - Observing cells with a microscope

Find out how to observe cells under a microscope

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Step by step

Image gallerySkip image gallerySlide 1 of 10, A picture showing a microscope an onion and glass slides., Click to see a step-by-step slideshow.
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Try the experiment online

Try out this experiment in Atomic Labs. Go to the Biology lab and try the Investigating onion cells experiment.

Atomic Labs game. game

Try out practical experiments in this KS3 science game

Atomic Labs game
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How to use a 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.

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Calculating magnification

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

Total magnification = eye piece lens magnification × objective lens magnification

For example: 10 × 20 = 200

Magnification = 200

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Working safely in the lab

Find out how to spot risks, hazards and understand hazard symbols

Working safely in the lab
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More on Living organisms

Find out more by working through a topic