Vanitas is an art theme. The word vanitas stands for vanity and emptiness. A vanitas artwork tries to transcend the futility of our earthly existence. Decay and the passing of time are often depicted by using skulls, dead animals, candles, withered flowers, rotten food, bubbles, faded books, clocks or overturned glass. The vanitas artwork has a Christian origin in which it encourages the viewer to focus on eternal life.
Source: https://en.wikipedia.org/wiki/Vanitas (derived 20-5-2016