Your microscope
What you see under the microscope · Onion
Onion cells under the microscope: what a plant cell looks like
A very thin layer from the inner face of an onion scale, on a slide and under a coverslip. It is almost every student's first microscopy practical.
Choose the microscope, the light and the technique in the panel.
40×: a network of compartments
With the 4× objective you can already see that the layer is made of elongated compartments, arranged like bricks.
100×: the walls
Each compartment is a cell, and the line around it is its cellulose wall, which gives the plant cell its shape.
400×: the nucleus
With the stain, the nucleus stands out as an oval next to the wall. Almost all the rest of the cell is taken up by a vacuole full of water, which is barely visible.
A plant cell, inside
Cut in half: the wall all around, the nucleus pressed against it and the large vacuole in the centre.
The microscope does not give you this 3D view: it sees a single plane.
Which microscope do you need to see this?
For onion, a biological microscope with 4×, 10× and 40× objectives is enough: it is the ideal practical to get started in class or at home.
Microscopes for schoolsWhich microscope do I need?Frequently asked questions
What can you see in onion cells under the microscope?
The cell wall surrounding each cell, the nucleus and, at higher magnification, the nucleolus. The vacuole fills almost the whole cell but, being transparent, it is barely visible.
What magnification do you need to see onion cells?
The compartments are already visible at 40×; the walls, at 100×; and the nucleus, clearly at 400×.
Why is onion stained?
Because without staining almost everything is transparent. Methylene blue or Lugol's iodine make the wall and the nucleus visible.
How this simulation is made
It is not a photograph: it is a calculated model. Magnification, field of view and resolution come from each microscope's spec sheet; the sample measurements come from the sources cited below.
| What | How it is calculated | What is approximate |
|---|---|---|
| Magnification and field of view | Magnification = eyepiece × objective. Field of view = eyepiece field number ÷ objective magnification. | Exact according to the spec sheet. |
| Cell size | About 300 × 70 µm, elongated like bricks. | School source; ±20% variation chosen by us. Layer thickness and nucleus size without a verified source. |
| Staining | Methylene blue: it defines the wall and the nucleus. | Colour chosen by eye. |
| Interior | Large central vacuole, cytoplasm in a thin layer against the wall and a disc-shaped nucleus with one to four nucleoli. | Granules placed at random. |
| Polarisation | The cellulose of the wall is birefringent: it shines depending on its orientation, and the stage rotates. | Approximate intensity. |
Sources
- Spec sheets of the Letscopes microscopes.
- Walter Dioni, “Onion epidermis”, Micscape (structures, stains and what you see at each magnification).
- Cell size: BioTopics.
- Methylene blue: Foldscope.
Other samples
Not sure which microscope to choose?
Tell us what you want to see and who it is for, and we will recommend the right instrument.
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