What does the black box in traditional epidemiology mean?

Traditional epidemiology often uses the "black box" theory to directly examine the relationship between exposure and disease or health when studying the relationship between exposure and disease. Although measures of morbidity and mortality can directly reflect the disease and health status of a population, the existence of the black box makes the relationship between exposure and disease appear to lack direct evidence. Molecular epidemiology, on the other hand, uses traditional epidemiologic methods to select study subjects, and applies molecular biology techniques to elucidate the distribution of biomarkers in the population and their relationship with disease/health and the factors that influence them at the molecular and genetic levels, so that the natural history of disease can be fully elucidated, i.e., the health-disease continuum and the exposure-morbidity continuum, and thus the "black box" can be revealed. This will help to reveal the "black box" secrets, formulate more effective strategies and measures for disease prevention and health promotion, and evaluate their effectiveness.