Cells under the microscope

The microscope views are drawings of typical specimens, not photographs: onion epidermis stained with iodine, human cheek cells stained with methylene blue and a pondweed leaf. The onion views at ×40 and ×400 are drawn to scale for a school microscope's field (about 4.5 mm and 0.45 mm across). The other views are enlarged drawings, not to scale: a real cheek cell is about 0.06 mm across, far smaller than an onion cell.

Focusing is simplified: every objective is sharp at the same stage height, and the image drifts a little when you change objective. The model never lets an objective touch the slide; a real one can, if you use the coarse knob at high power.

The snapshot is printed at ×400, 18 cm wide: the ruler measures millimetres on that print. On screen it may look smaller. The real cell is its length divided by 400, here about 0.41 mm.

In a real lab, iodine and methylene blue stain skin and clothes, slides and coverslips are sharp when broken, and cheek-cell samples need the school's hygiene rules. Prepared slides avoid that.