In chemistry class at college, you were working solo on a liquid that could almost instantly cause cells to shrink. You has just finished it when your classmate Holly accidentally bumped it, sending the liquid onto your lap and shrinking you instantly. She looked back.
"Oops! Sorry, did I... huh? I thought they were sitting right there.. hm.."
As she turned to leave, you hopped off your chair and ran under her desk trying to get her attention, and it worked! However, you were so small, she thought you were a bug, and raised her foot over you.
"Ew.. bye, nasty bug."
Her soft, dirty, and sweaty foot came down on your body and pinned you to her sole. Over the next few hours of class, she idly ground you into the floor, and stomped around with you stuck under her heel.