Hi Andreas, you ask a truly salient question. As mentioned in my post, aSquared Nutrition is an FDA registered facility, all of their products are made in the United States and are compliant with GMP (Good Manufacturing Practice) regulations under the authority of the Federal Food, Drug, and Cosmetic Act. These regulations, which have the force of law, require that manufacturers, processors, and packagers of drugs, medical devices, some food, and blood take proactive steps to ensure that their products are safe, pure, and effective. aSquared does make the claim that their products undergo rigorous testing to ensure quality and reliability. That said I did not see a certificate of strength and purity for their Resveratrol on their website or in any of my research on the company.