When you live in locations where you do not live under heat and A/C every moment of the day, you often find yourself putting things is Tupperware (or something else hermetically sealed) as soon as you open it. Flour. Cornstarch. Sugar. One year I had cornstarch and confectioner's sugar in similar containers that I did NOT label. A couple of times I tried to thicken my stir fries with confectioner's sugar. Ironically, they were very, very popular, my friends and family having much more of a sweet tooth than I! Duh!