A Happy American Lotus
The smiling face in this photo is made of water drops on the surface of a lotus leaf. Lotus leaves are considered super-hydrophobic — they repel water strongly, causing it to bunch up into discrete drops with well-defined edges.
While the leaf appears smooth to the naked eye, it is actually covered with bumps and hairs of nanoscale size. Water doesn't touch the actual leaf surface. Instead, it only touches the tiny hairs, and surface tension causes the water to ball up into smooth-edged drops.
We humans may get a cute smiling face photo, but what benefit does the lotus get from its water-repelling abilities?
Consider washing a car. If the car is waxed, water beads up and rolls off, and the car looks nice and clean after it dries. But without wax, water forms wide sheets that evaporate, leaving unsightly watermarks.
A lotus leaf is similar to a waxed car. Water beads up, rolls off, and keeps the leaf clean. This is of great benefit to the lotus, as dirt on its leaves reduces the efficiency of photosynthesis.
As a result of its ability to stay clean in the muddiest of lakes, the lotus is considered a sacred symbol of purity in some cultures.