Hourglass is a night light that has very simple function of dimming light without adding other layer of technology. By flipping its body upside down, the sand will trickle down and cover the light source. It is consisted of two 3V lithium battery, LED light and weight sensor. Weight sensor is connected to LED lights and programmed to understand total weight of sand. Therefore once the entire sand trickles down, it is programmed to turn off the LED lights so that you don't actually waste your battery.
If you want to switch them up, just push the lid down and there is a slight slope that allows the lid to open up. The lid is held together by hidden magnet.