Dr. Miguel A. Hernán, professor of epidemiology at Harvard T.H. Chan School of Public Health, discusses target trial emulation for causal inference from observational data with JAMA Statistical Editor. They explore the concept of target trial emulation, the importance of randomized clinical trials, estimating the effectiveness of Tocilizumab in ICU patients with COVID-19, and the complementary role of randomized trials and observational studies in generating evidence.