Each Post-It note has a strip of pressure-sensitive adhesive on the back. The adhesive enables notes to stick to a surface, but it does not bond too tightly so notes can be easily removed. The exact composition of Post-It adhesive is a closely guarded secret but chemists who have studied it believe the glue contains microscopic bubbles. These bubbles rupture under pressure, creating tiny vacuums that act like suction cups to stick the note to a surface. The notes will continue to stick after multiple uses until all the bubbles have been burst so no further vacuums can form.
