Baubles by Kaia Nao
The four spheres (which the artist calls baubles) appear to be moving. If you move your eyes rapidly around the image, you will find that the motion effect is enhanced.
A larger, single bauble version of this image can be found below.
To see more motion illusions from Kaia Nao, please check out Floating Star Illusion and Schmear.
(via Kaia Nao)