Starry Night (1888) by Vincent van GoghMusée d’Orsay, Paris
Nighttime is always happening somewhere in the world and most people use that time to sleep. Curl up under a blanket and scroll on to discover facts about slumber.
Cat Asleep (17th century) by Cornelis de VisscherDavison Art Center, Wesleyan University
Sleep is a necessity for all mammals and almost every other animal. In fact, sleep has even been observed in some insects!
This 17th century Cornelis de Visscher etching shows a cat asleep while a brave mouse sneaks behind it.
Two Sleeping Children (c. 1612-13) by Peter Paul RubensThe National Museum of Western Art, Tokyo
Do you dream when you doze? Most people dream a few hours a night, but may not remember. People throughout history have interpreted dreams differently, depending on the time and place.
Rembrandt van Rijn, Young Woman Sleeping, a drawing (1654/1654)British Museum
Before the industrial revolution, research suggests that many people slept in two periods during the night--getting up for a short period before going back to bed. Many languages even have terms meaning "first sleep" and "second sleep."
The introduction of artificial light and longer hours may have led to the decline of this practice. Rembrandt sketched this drawing of his slumbering wife in 1654.
La Siesta (1911) by Joaquín Sorolla y BastidaSorolla Museum
In many cultures, it is still customary to take a midday nap. In 1911, Spanish artist Joaquín Sorolla painted his family taking a siesta in the grass. Do you nap during the day?
The Dormition of the Virgin (c. 1490) by Ferrarese painterVeneranda Biblioteca Ambrosiana
Some Christians observe the Dormition of the Virgin, as depicted in this 1490 painting, celebrating Mary's spiritual ascension to Heaven. Shakespeare wrote, "For in that sleep of death, what dreams may come."
By John DominisLIFE Photo Collection
Sleep is not always possible, as shown by actor Steve McQueen's pet malamute. When people don't get adequate sleep, they take on what is known as sleep debt, which causes fatigue and takes a toll on cognition.
Mission Specialist (MS) Ride sleeps in airlock (1983-06-24)NASA
Even people in outer space have to sleep! This snapshot is of American astronaut Dr. Sally Ride using a sleep restraint to prevent floating away. Can you imagine drifting off while weightless?
The Sleeping Beaty by Rudolf Nureyev (Marie-Agnès Gillot) (1999) by OnPOpéra national de Paris
Feeling sleepy yet? If you're still awake, you can watch a video from Tchaikovsky's longest ballet, The Sleeping Beauty. Sweet dreams.