anything, as long as it's small

Strain Solitons and Topological Defects in Bilayer Graphene

$Bilayer graphene: Three DF-TEM images taken from the diffraction angles indicated in the inset are overlaid in red, blue, and green.$

Jonathan S. Alden, Adam W. Tsen, Pinshane Y. Huang, Robert Hovden, Lola Brown, Jiwoong Park, David A. Muller, and Paul L. McEuen

PNAS 110, 11256-11260 (2013)