Designer drugs are synthetic analogs of illegal substances that are modified slightly to circumvent drug laws but produce similar effects. They emerged in the 1900s and gained popularity in the 1960s-1990s, especially in clubs. Examples include synthetic stimulants like bath salts, synthetic cannabinoids like Spice, and synthetic hallucinogens. Designer drugs are marketed as "not for human consumption" but their vague wording and constant modifications allow unlimited manufacturing until they are eventually made illegal through legislation.