"LSD (d-lysergic acid diethylamide)—also known as acid, blotter, doses, hits, microdots, sugar cubes, trips, tabs, or window panes — is one of the most potent moodand perception-altering hallucinogenic drugs. It is a clear or white, odorless, water-soluble material synthesized from lysergic acid, a compound derived from a rye fungus. LSD is initially produced in crystalline form, which can then be used to produce tablets known as 'microdots' or thin squares of gelatin called 'window panes.' It can also be diluted with water or alcohol and sold in liquid form. The most common form, however, is LSD-soaked paper punched into small individual squares, known as 'blotters.'"

Source

"Hallucinogens and Dissociative Drugs, including LSD, PCP, Ketamine, Dextromethorphan," National Institute on Drug Abuse Research Report Series (Rockville, MD: U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, 2001), p. 3.