Now lay your hand on a flat surface and it feels like you are touching a convex surface, like the surface of a ball. Amazingly, the illusion might even work for the other hand (the one you didn't ...

In these studies, the reported surfaces are still macroscopically flat, with the feature size at the scale of microns or nanometres. In nature, many plant surfaces have convex or concave ...

When light bounces off of a flat surface ... like a contact lens. The convex shape extends the focal point so that light striking the curved surface from a wider swath of angles all converge ...