Heroin is a drug that comes from a flower, the opium poppy, which usually grows in Mexico, Asia, and South America. It’s very addictive and has been illegal in the United States since 1924. It can look like a white or brown powder, or a sticky black “tar.” It’s also called horse, smack, junk, and brown sugar. Many people smoke or snort heroin. Most users inject it into their veins. That’s the most dangerous way to take it, because it’s easier to overdose and you can catch a disease from a dirty needle. No matter how you take it, heroin gets to your brain quickly. It’s also easy to get addicted. Even after you use it just one or two times, it can be hard to stop yourself from using again.