Instructions For Onion Cell Slides
More than 300 years ago, Robert Hooke used a microscope to look at thin slices of cork and called the structures that he saw "cells." Today, in school science labs, looking at onion skin slides with a microscope is a common way to introduce students to the concept of cells. The thin membrane on the inside of the rough onion skins is thin enough to allow light through and to be visible under the microscope. The membrane also readily stains, which makes it possible to clearly see the cell wall, cytoplasm and nucleus.
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Things You'll Need
- Microscope
- Lens paper
- Slide
- Coverslip
- Tweezers
- Eye dropper
- White onion
- Knife
- Stain: iodine or 1 percent methylene blue
Instructions
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1
Polish the slide and coverslip with lens paper.
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2
Use an eyedropper to place a drop of stain in the middle of the slide.
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3
Cut the onion in half and remove course outer skins.
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4
Using tweezers, locate the thin membrane between the skins and meat of the onion.
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5
Place a small piece of membrane in the middle of the slide on the drop of stain. Use tweezers to carefully flatten it out.
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6
Add another drop of stain to the top of membrane.
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7
Place one edge of the coverslip on the slide and slowly lower it onto the membrane. Use tweezers to gently tap out any bubbles.
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8
Set the microscope at the lowest magnification. Place the slide on the microscope stage. Focus with knobs on the side.
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1
Tips & Warnings
Iodine and methylene blue can stain hands and clothing.
Do not increase magnification of microscope while looking through the lens -- always watch from the side to make sure you do not break the slide.
References
- Photo Credit Ablestock.com/AbleStock.com/Getty Images
