Abstract Topological defects, which play crucial roles in systems ranging from morphogenesis to energy guidance and information storage, are of fundamental interest across many branches of physics. Programmable control of such defects through external stimuli enables the active manipulation of material properties, thereby facilitating the precise tailoring of their functional behaviors and responses. This review systematically elucidates the central role of topological defects in directing the evolution of liquid crystal (LC) ordered structures under external stimuli and across phase transitions. We first analyze the stimulus‐responsive dynamics of defects in nematic LCs, focusing on light‐induced reconfiguration, electric‐field‐driven transformation, and their guidance of collective behavior in active colloids and bacterial systems. We then explore the defect‐mediated order evolution during the nematic‐smectic A phase transition, detailing how nematic defects transform into functional smectic architectures. Moreover, the self‐assembly strategies, morphological transitions, and theoretical modeling of two typical textures of smectic LCs, focal conic domains (FCDs) and oily streaks (OSs), as well as their deformation forms, are systematically exhibited; applications of FCDs and OSs in photonics, micro/nanofabrication, and particle assembly are demonstrated. By integrating recent advances in defect programming, phase transition regulation, and responsive materials design, this review establishes a unified framework for the dynamic control of topological‐defect‐featured ordered structures across scales, bridging fundamental topology with functional innovation. These significant progresses extend our knowledge of self‐assembled architectures and make a solid step forward in the sciences and technologies of smart materials and corresponding applications.
Wu et al. (Sun,) studied this question.