Quantum Vacuum :

The words "nothing," "void," and "vacuum" usually suggest uninteresting empty space. To modern quantum physicists, however, the vacuum has turned out to be rich with complex and unexpected behaviour. They envisage it as a state of minimum energy where quantum fluctuations, consistent with the uncertainty principle of the German physicist Werner Heisenberg, can lead to the temporary formation of particle-antiparticle pairs.

Excerpt from the Encyclopedia Britannica without permission.