Cell wallThe lines that box each cell in. Onion skin cells are joined wall to wall, which is why they keep their long box shape.
NucleusA small round body in each cell. A drop of iodine stains it, which makes it easier to see.
CytoplasmEverything between the cell wall and the nucleus. There are no chloroplasts in it: an onion bulb stores food and does not photosynthesize.
Cheek cells 3
Cell membraneA cheek cell has no cell wall. Its thin cell membrane is its only boundary, so the cell is flat and irregular in shape.
NucleusThe body near the middle of the cell. It takes up stain more deeply than the rest of the cell.
CytoplasmThe rest of the cell, between the membrane and the nucleus. Old school books call it the cell body.
Elodea leaf 3
Cell wallEach brick-shaped cell is boxed in by its cell wall.
ChloroplastThe small bodies that hold the chlorophyll. In a living leaf they drift round the cell, carried by the moving cytoplasm. Old school books call them chlorophyll bodies.
Central vacuoleThe clear middle of the cell, filled with cell sap. The chloroplasts lie outside it, near the wall.
How this list was compiled: Every part was checked on 2026-09-30 in two places, for facts only and with nothing copied. (1) G. W. Hunter, A Civic Biology (1914), https://archive.org/details/civicbiologyprob00huntrich, and his Laboratory Problems in Civic Biology (1916), https://archive.org/details/laboratoryproble00huntrich. (2) J. E. Peabody and A. E. Hunt, Elementary Biology (1912, printing of 1921), https://archive.org/details/elementarybiolog00peabrich. Both are public-domain school books that set these three slides as one lab. They call the cytoplasm protoplasm or the cell body and the chloroplasts chlorophyll bodies; the modern names were checked in (3) Wikipedia, text only, Onion epidermal cell, https://en.wikipedia.org/wiki/Onion_epidermal_cell; (4) the National Cancer Institute SEER training module on cell structure, https://training.seer.cancer.gov/anatomy/cells_tissues_membranes/cells/structure.html, and Florida State University's Molecular Expressions plant cell page, https://micro.magnet.fsu.edu/cells/plantcell.html; and (5) two journal abstracts read through Europe PMC, https://europepmc.org/article/MED/42119475 (cheek cells) and https://europepmc.org/article/MED/25959623 (Elodea). Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
This onion cell diagram shows what the microscope shows: long cells joined wall to wall, each with a nucleus. Two more views give the other slides of the same lab, cheek cells and an Elodea leaf.
Read the full guide
Onion skin, then a cheek cell diagram
Onion skin cells have a cell wall, so they keep a box shape and fit together. Cheek cells have none: each is flat and irregular, held only by its cell membrane. The second view is a human cheek cell diagram, drawn from cells that line the inside of the mouth.
What the Elodea cell diagram adds
Elodea is a water plant. Its leaf cells show what onion skin lacks: chloroplasts. They sit round the edge of each cell, outside a clear central vacuole.
A drop of iodine stain makes the nucleus easier to find in onion and cheek cells.
In a living Elodea leaf the chloroplasts drift round the cell. Let the slide stand in a warm place and watch.
Questions and answers
Why do onion cells have no chloroplasts?
The cells come from the bulb, which stores food and does not photosynthesize. Elodea leaf cells do photosynthesize, and they are full of chloroplasts.
What is the difference between an onion cell and a cheek cell?
An onion cell is a plant cell: it has a cell wall and a regular box shape. A cheek cell is an animal cell: it has no wall, only a cell membrane, and an irregular shape. Both have a nucleus and cytoplasm.
What parts of an onion cell can you see under a light microscope?
The cell wall, the nucleus and the cytoplasm. A stain such as iodine makes the nucleus stand out.
What are the small bodies round the edge of an Elodea cell?
Chloroplasts, which hold the leaf's chlorophyll. Older school books call them chlorophyll bodies.