Flying butterflies

There is a hint in the title of the painting

A stereogram is an image made in such a way that with a special technique of viewing (focusing the eyes) it becomes three-dimensional. Thus, in a two-dimensional picture, three-dimensional objects can be seen.
"Reading" stereograms is a wonderful gymnastics for the eyes, as it has the ability to relieve tension, relax the eye muscles, the main thing, like everywhere else and in everything, is not to overdo it.
Bring the picture to the very tip of your nose. Relax your vision and look straight ahead. Now begin to slowly move the picture away until you reach the distance you would normally hold the book at when reading. First, the drawing will blur before your eyes. However, it is worth looking into it more closely, and soon you will have a clear three-dimensional image before your eyes.