Your favorite teacher could really use a ripe apple and sometimes, with some fruit and vegetables it can be tricky — OK not if you were born on a farm — detecting whether or not the fruit or vegetable is ripe. A University of Arizona Professor has invented (patent pending) a sticker that could help with this problem.

A marker on Riley’s RediRipe stickers detects a chemical called ethylene gas, which is released by fruit or vegetables as they ripen. As that happens, the sticker turns from white to blue. The more ethylene gas the fruit produces, the darker the blue, Riley said.

No more melon squeezing?