[GIST과학주간 기초교육학부 강연시리즈1]  In the Newtonian framework, the future trajectory of a physical system can be determined from its initial conditions using the equations of motion. However, the power of this formalism is limited to one- or two-body systems. For three or more bodies, the dynamics become chaotic, making precise predictions impossible. So, how do physicists calculate the properties of many-body systems, such as chemical mixtures or electronic devices? In this seminar, I will introduce the formalism of statistical mechanics, which tames chaotic behavior through combinatorial state number counting. I will also briefly explore recent developments that have deepened our understanding of nonequilibrium systems.