Take a clean cotton swab and gently scrape the inside of the mouth. Smear the cotton swab on the centre of the microscope slide for 2 to 3 seconds.

Add a drop of methylene blue solution and place a coverslip on top. then visualized under foldscope.

Methylene blue stains negatively charged molecules in the cell, including DNA and RNA. This dye is toxic when ingested and it causes irritation when in contact with the skin and eyes.