"Hourglass"

An hourglass is a device used to measure time. It consists of two connected glass bulbs filled with sand. When the upper bulb is turned upside down, the sand flows through a narrow passage to the lower bulb, taking a set amount of time to do so. Once all the sand has moved to the bottom, the hourglass can be flipped to start the timing process again. Although traditional in design, hourglasses symbolize the passage of time, and their visual appeal has made them popular as decorative items and teaching tools in various contexts.