Dr. Lindsey Mackay is General Manager at the National Measurement Institute in Australia. She tells us what reference materials are, how they are used in drug testing labs, why they are critical for anti-doping, how they are made, how they are distributed, and more. She also shares major challenges in making reference materials and a recent project in which they created new reference materials to differentiate between testosterone-related steroids from external sources versus made naturally by the body.