Smoking is the most common method of consuming tobacco, and tobacco is the most common substance smoked. The agricultural product is often mixed with other additives and then pyrolyzed. The resulting vapors are then inhaled and the active substances absorbed through the alveoli in the lungs. For more information go to the website of the The Legacy Tobacco Documents Library (LTDL) at http:legacy.library.ucsf.edu . The Library contains more than 10 million documents (50+ million pages) created by major tobacco companies related to their advertising, manufacturing, marketing, sales, and scientific research activities. This is clipped from the film, Care for a Smoke? Produced by Philip Morris Europe. The film explains the cigarette making process, focusing on research and development. The entire film is available at the Internet Archive.
It starts a little slow for the first few minutes, but if you enjoyed this brief excerpt, you'll probably really enjoy most of the rest of the film.
One of the nice things about this piece is that it provides a nice overview of tobacco types, curing, casing and top dressing (flavoring), as well as processing and blending, all of which are great background for understanding and selecting tobacco blends for make your own (MYO) cigarettes.