Material (fig 1):

Microscopic slides;

Cover slip;

Tweezers;

Optical microscope;

Onion for the purposes of obtaining an epithelium (taken from onion cataphyll at the moment of the experiment);

Stain - methylene blue or neutral red or acid fuchsin – diluted stain (0.1% solution).

Note: Lugol's stain can be used to stain the nucleus: 100g distilled H2O + 6g potassium iodide + 4g de iodine.

Figure 1: Materials necessary for this experiment.