This is what the surface of a tomato plant leaf looks like under extreme magnification:
Those hair-like structures are called “trichomes.” Many plants have them and they serve a variety of functions, depending on how they grow and serve the survival of the plant. On a tomato leaf, seen here, a certain type of trichome helps reduce the evaporation of water by trapping droplets on the surface of the leaf.
If you grow tomatoes, you may have noticed that some parts of the stems and leaves feel sticky. That’s due to other types of trichomes, working to protect the plant from hungry critters. It’s thought that these specialized trichomes produce oils and crystals that smell, feel, and taste unpleasant. So a hungry beast may think twice before taking a bite of the yummy red fruit, lest it get a mouthful of bitter stem and leaf.