There are supermarkets whose doors are open around the clock. Jewel, which is one of the largest supermarket chains in the United States,keeps some of its stores open 24-hours on Mondays through Saturdays. If you shop at any of these stores in the early hours of the morning,you might be surprised at the number of grandmothers and mothers with small children. Many supermarkets that stay open 24-hours are located near highways,but this is changing. There are already some towns where even the smaller chains stay open for longer hours.