Deja vu is a French phrase meaning 'already seen,' referring to the distinct, puzzling, and mysterious feeling of having experienced a specific set of circumstances before. A woman might walk into a building, for example, in a foreign country she'd never visited, and sense that the setting is eerily and intimately familiar. Some attribute deja vu to psychic experiences or unbidden glimpses of previous lives. As with intuition, research into human psychology can offer more naturalistic explanations, but ultimately the cause and nature of the phenomenon itself remains a mystery.