Abstract: A container having an expandable thickness for better insulation. The container has two walls which may be expanded to form an insulating air space therebetween. The expansion may be caused by compressible foam, an expandable strip material, a projection running on an inclined surface arrangement or by a gas generating material. The expansion may be activated by removing a vacuum, pulling a physical strip, by rotating one layer within the other or by crushing microcapsules to release gas. The expanded container provides better insulation for hot foods but allows a smaller thickness for storage.