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Two ways to see it

Necker cube

A simple line drawing of a cube flips between two different 3D shapes.

By Illusions Blog · Updated · How we make them

TypeTwo ways to see it
InteractiveYes: sliders and a check
First described1832

Look for a while: the face that seemed to be in front jumps to the back, and the cube flips.

Try this

  • Tick Shade one face to make that face the front; then try the other.
  • Focus on one corner and try to flip it at will.

Why it happens

The drawing fits two 3D cubes equally well, and the brain cannot hold both at once, so it switches between them. Louis Albert Necker, a Swiss crystallographer, described it in 1832 after noticing crystals in drawings flipping orientation. Researchers use it to study how attention and expectations steer what we see.

Did you know?

You can usually speed up the flipping by moving your eyes between corners.

References

  • Necker L. (1832). LXI. Observations on some remarkable optical phænomena seen in Switzerland; and on an optical phænomenon which occurs on viewing a figure of a crystal or geometrical solid. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 1, 329-337. doi:10.1080/14786443208647909
  • Background on Wikipedia

The illusion on this page is drawn by code written for this site. Last checked 1 November 2026.

Frequently asked questions

Why does the Necker cube flip?

The drawing fits two 3D shapes equally well, so perception alternates between them.

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