Yes, get the red onion- the red pigment in the cells make them easier to visualize with the microscope. To prepare- cut the red onion into wedges. Do not use the “dead”, dry outer layers. From one of the inner layers, peel off a thin layer from a red portion of the onion. It does not have to be long (few millimeters will suffice), but it must be thin! You can do this with metal tweezers but finger nails will also work (kids have done it in our class room with their fingernails. Try to make it think, but it does not have to be perfect. You will see onion cells! Spread the thin onion layer on a glass slide. Looks best at 60X with bottom illumination (if reasonably thin) . Also can check it out at 200x.

 

Watch onion cells shrink and expand. See "Osmosis in Action".

You will need to order a dye to stain the nuclei, which stains the DNA. I put on ONE drop of “Fast Green” stain directly on top of the onion slice. For elementary school kids, I recommend that you handle the stain and putting on the drop yourself (potential skin toxin).

You can buy Fast Green and several other stains from Carolina Biological for ~$60 (Catalogue #89-2261).