The digital image below shows trichomes on a leaf of Verbascum thapsus, better known as the common roadside mullein plant. Trichomes are minute, highly specialized outgrowths that can be found along any surface of a plant and are designed to enhance a plant's chances of survival.

These accessory structures occur most often along stems and leaves, but they can also be found on the surface of petals and comprise the fragrant and sweet nectaries that draw pollinating creatures. Many forms of trichome help adjust the microclimate on the surfaces of the leaves by reflecting solar radiation and preventing evaporation of critical water supplies. Trichomes that manifest curly shapes are developed for use as reflectors by such plants as the desert brittlebush. Each variety of plant produces trichomes that are most suited to cope with the conditions of its environment. Although various forms exist, these appendages commonly occur as glandular, nonglandular, scales, papillae, or hair-like structures.

Glandular trichomes contain volatile oils as well as other secretions that can cover the surrounding surface of the leaves and petals. Aromatic plants (such as lavender) as well as culinary herbs (mint, sage, thyme) store essential oils in globe-shaped head cells. Some trichomes have specifically evolved to act as defense mechanisms. Trichome structures that occur in large numbers may protect a plant by making its tissue less edible or hospitable to feeding and breeding insects. Several plant varieties form glandular structures that produce chemicals that are poisonous to insects that contact, ingest, or even inhale trichome secretions. The catchfly plant produces a sticky substance that adheres to and traps unsuspecting insects. Strategically located to minimize nibbling from pests, trichome structures typically lie in greater numbers along the edges of leaves. When trichomes grow in abundance, they cause leaves to have a fuzzy appearance.