See if you can find the 8 differences in each set of images.

Photonic crystal

This is a reflected image of a localized defect in a one-dimensional photonic crystal. The inclusion of a dust particle causes uneven layer thicknesses. These uneven layers reflect an array of vibrant colors. This image was not altered with Photoshop. It was taken using a modified optical microscope, coupled with a CCD camera.

Wendy J. Nimens, The University of Utah, USA.

figure 1

Multigenerational wrinkles

Mechanical deformation results in sequence-dependent surface topographies with structural memory.

figure 2

Po-Yen Chen, Brown University, USA.

figure 3

Answers will be published in the August 2017 issue.