Many types of trichomes are found on the stem of the tomato plant. Among the most interesting are the multi-cellular glandular trichomes which often contain crystals. Tomato glandular trichomes of this type have been found to contain crystals composed of calcium oxalate and cadmium oxalate. Essential oils are often stored in the bulbous region of these structures as well, giving the plant its characteristic odor and sticky texture. Both crystals and essential oils may serve as defenses against herbivory.

Notice the crystal in the bulbous region of these two trichomes

Hairs