That old saying "don't cry over spilt milk" may soon go the way of the dodo, if the ever-expanding wheels of science have anything to say about it. A team of Chinese researchers have invented something they are calling smart-tags. These tiny gel-like tabs can be affixed to just about any perishable food stuffs, from canned products to jugs of milk.

How does it work? Each tag is made from the futuristic sounding nanorods, that are actually made out of gold and silver (they are still cheap to produce.) Each microscopic rod also contains a series of compounds that change color depending on what stage of development your can of soup is in. Red means the food is super fresh and if it traverses the rainbow and ends up on purple, your stomach is in for a world of hurt.

These tabs are making their rounds in science journals, so they could be a long ways off from seeing store shelves. In the meantime, just don't drink milk that is green and thicker than cottage cheese.