Usually, people think that illusions are funny and interesting, but they always take us away from reality. In this talk, I will introduce illusions from another point of view. We will see, that certain sensory illusions are not just useful, but essential for our survival. Even further, modern safety solutions often use these illusions to save our lives. The presentation will summarize results of experiments using ventriloquism, out-of-body experiences and distance illusions; to conclude that illusion might not take us away from reality after all.