CHEMICAL BREW-HAHA: The chemical 1,3,7-trimethylxanthine is so potent in its purified form that lab technicians who work with it must wear masks and gloves. The chemical warrants the following warning label: "May be harmful if inhaled or swallowed. Has caused mutagenic and reproductive effects in laboratory animals. Inhalation causes rapid heart rate, excitement, dizziness, pain, collapse, hypotension, fever, shortness of breath. May cause headache, insomnia, nausea, vomiting, stomach pain, collapse and convulsions." You won't see such a warning in your local coffee shop, even though