Jellyfish Sleep, and Now Scientists Wonder If Plants and Bacteria Sleep Too

The discovery that jellyfish go to sleep is making scientists rethink when sleep first evolved, what it actually is, and how it helps us and other snoozers.

September 21, 2017
12:00 PM EDT
“If jellyfish dream, what would they dream about?”
Caltech footage of the jellyfish Cassiopea.
Multiple Cassiopea jellyfish. The animals prefer to sit upside down on the floor of the water column. | Caltech