Heredity underlies the stability of an organism's fundamental phenotype. The complex interaction between genetic variation, epigenetic modification, microbial and environmental factors, and biological inheritance determines the phenotypic differences of each individual and those of the same individual at different life stages, reflecting the robustness and complexity of biological processes. The central challenge in modern biology is to distill these complexities into a discernible cognition distinguishing "self" from "non-self". As a response to this challenge and a growing demand for comprehensive intersection of future science and technology, we propose the concept of Flag Biology, which represents a novel discipline that, by employing the latest technology and comprehensive investigation, teases out complex biological processes into minimalist knowledges in a quantitative and characteristic way.