Credit: R. Press/NIST After weighing this package of marijuana, NIST research chemist Brent Wilson ground up the contents to prepare samples with very precisely measured amounts of THC, CBD and other compounds. Those samples will be sent to labs as part of a study that will help labs improve their measurement accuracy. Labs that are not licensed to handle controlled substances will receive samples of hemp instead of marijuana. Hemp and marijuana both come from the Cannabis plant. But legally, they are very different. If cannabis has less than 0.3% THC – for tetrahydrocannabinol, the chemical that produces a high – it is considered hemp and legal throughout the United States. Otherwise, it’s marijuana and currently treated as a controlled substance by the federal government and many states.