Cannabis smoking is the process of inhaling the vapors release by combusting cannabis. Most frequently the flowering buds of the cannabis plant, or hashish, a preparation of the trichomes of the cannabis plant, are used. Lighters, matches, or solar power through a magnifying glass can be used to combust it. Cannabis is almost exclusively consumed to produce a feeling of euphoria, though it is also consumed for other medical reasons (such as to relieve stress). During this process, the main psychoactive chemical in cannabis, Δ9-tetrahydrocannabinol (THC), is absorbed into the bloodstream through the lungs. It is then transported to the brain, where it binds to cannabinoid receptors, a type of protein cell in the brain. The cannabinoid receptors receive the THC, setting off a chain reaction that leads to the feeling of a mental "high". It has also been found that heating of cannabis results in the production of additional THC from the decarboxylation of the non-psychoactive Δ9-tetrahydrocanabinoid acid (THCa).