these are some pretty water beads on cattail leaves. or if you prefer to think of it another way . . . materials with a special affinity for water — those it spreads across, maximizing contact — are known as hydrophilic. those that naturally repel water, causing droplets to form, are known as hydrophobic. both classes of materials can have a significant impact on the performance of power plants, electronics, airplane wings and desalination plants, among other technologies. you can pick one or the other.