Trichomes are microscopic protrusions consisting of a stalk and a head found throughout the cannabis plant's buds, fan leaves, and stalk. Within the heads of these protrusions, therapeutic cannabinoids and terpenes are produced. There are three types of trichomes: Bulbous, capitate-sessile, and capitate-stalks. While it is relatively unknown how the types differ from each other, it is believed that all types of trichomes produce all terpenes and cannabinoids.
When trichomes receive UV light, cannabinoids are produced. This explains why plants that receive light of the proper wavelength, intensity, and duration, produce more cannabinoids. While it is a good sign to see a large amount of tiny trichomes on the cannabis plant, it does not necessarily mean the glands themselves contain hight amounts of cannabinoids and terpenes. Large amounts of trichomes does not guarantee the plant will be more effective medicinally. The color of a trichome generally develops from clear to white to an amber brown, indicating the maturity of the plant and the effect it will have.
As far as vehicles and substances are concerned, the core material of extracts and concentrates is made up of trichomes. Whaxy says, "Despite celebration of the plant's green leaves and buds, it is actually the nearly invisible sugary crystalline trichomes that provide all medical and recreational value. Patients must remember that it isn't the lovely green plant matter in their bowl or joint that is providing them with relief, but rather the sprinkling of resin glands in which are suspended compounds like THC and CBD."
Read in detail about microscopic trichomes from Whaxy.