In this book you will find 51 stereograms (3D relief images) . They are regularly used by orthoptists in order to re-educate the eyes of their patients. Both playful and practical you may spend from several minutes to several hours to discover all the 3D images. Practice and if you doubt an image or if you can't see it, don't worry, all the solutions are at the end of the book! Show it also to your friends and family, children and grown up , in order to test their ability to see beyond the visible. Take your time! Soon, the reliefs of the stereograms will have no more secrets for you.