Smoking is a practice in which a substance is burned and the resulting smoke breathed in to be tasted and absorbed into the bloodstream. Most commonly the substance is the dried leaves of the
tobacco plant which have been rolled into a small square of rice paper to create a small, round cylinder called a "
cigarette". Smoking is primarily practiced as a
route of administration for
recreational drug use because the
combustion of the dried plant leaves vaporizes and delivers
active substances into the lungs where they are rapidly absorbed into the bloodstream and reach bodily tissue. In the case of cigarette smoking these substances are contained in a mixture of aerosol particles and gasses and include the pharmacologically active alkaloid
nicotine; the vaporization creates heated aerosol and gas to form that allows inhalation and deep penetration into the lungs where absorption into the bloodstream of the active substances occurs. In some cultures, smoking is also carried out as a part of various rituals, where participants use it to help induce
trance-like states that, they believe, can lead them to "
spiritual enlightenment".