Look up from this page and scan the scene in front of you. Your eyes dart around, bringing different objects into view. As you read this article, your eyes jump to bring every word into focus. You can become aware of, and even control, these large movements of the eyes, which scientists call saccades. But even when your eyes are apparently fixed on something—say, on a tree, face or word—they are moving imperceptibly, underneath your awareness. And recent research shows that these minute, subconscious eye movements are essential for seeing.