Have you ever followed a slimy, iridescent trail in the garden or park and found a snail, munching on a tasty plant? Or maybe a slug was helping itself to your snap peas! Snails and slugs look pretty similar, so why does only one have a shell? We asked biologist Teresa Rose Osborne to help us track down the answer.

Got a question that has you retreating into your shell? Send it to us at BrainsOn.org/contact, and we’ll try not to answer it at a snail’s pace!