According to Wikipedia, a Necker cube is an optical illusion first published in 1832 by Swiss crystallographer Louis Albert Necker.

Here's one example of a Necker cube:

Given a little time, most people see this image in two different ways. Pay attention to how the red dot sometimes appears in the near corner and sometimes appears in the far corner.

Or you may prefer a colorless Necker cube:

Believe it or not, these variations in perception are extremely relevant for how you lay down memories in your mind. Michael Lovitch will address this topic in the next issue of the newsletter.

NOTE: To see both options, you may need to look at either of the images for at least a couple of minutes. It may also help to stand away from the computer and look at your selected image from different angles.

published in the January 16, 2007 issue of Exploring the Mind, the Hypnosis Network's email newsletter