PlanetBox is not designed to retain heat – it does not keep hot foods hot. You can place warm food (not boiling hot liquid) inside your PlanetBox in the morning, and it will be room temperature by lunch time. Also, some customers successfully use PlanetBox in their child’s hot lunch line at school. They send an empty PlanetBox in the morning, and their child brings home their PlanetBox in the afternoon to wash – no trash created! If you plan on putting warm foods in the Dippers, allow them to fully cool before placing the top on them. Putting warm foods in the Dippers and putting the top on them can cause a vacuum seal to be created, which will make the top of the Dipper very difficult to remove. If this occurs, you need to chill down the bottom of the Dipper and warm up the top, and that should help break the vacuum seal. You can only us the glass Satellite Dish with your Launch Lunchbox to reheat foods in the microwave or oven.