Yi-Fang Chang Department of Physics, Yunnan University, Kunming, 650091, China yifangch@sina.com International Journal of Fundamental Physical Sciences (IJFPS) 10 2 16-26 June, 2020 2231-8186 https://doi.org/10.14331/ijfps.2020.330137 This paper challenges the universal applicability of the second law of thermodynamics by exploring conditions under which entropy may decrease in isolated systems. The author examines scenarios involving internal interactions, fluctuations, phase transitions, self-assembly, molecular motors, and biological, chemical, astronomical, and social systems. A universal entropy change formula is proposed. The paper posits that, by relaxing certain assumptions of thermodynamic isolation and equilibrium, entropy reduction can explain the emergence of order in complex systems, contradicting the dogma of inevitable disorder. Entropy, Internal interaction, Isolated system, Condensed matter, Self-assembly, Solidification, Molecular motor, Biology, Astronomy https://creativecommons.org/licenses/by-nc/4.0/