Over the past couple of decades, various stimuli-responsive organic molecules have been developed as a result of remarkable advances in synthetic and material sciences (Fig. 1.1) (Wei et al. in Polym. Chem. 8:127–143, 2017;Hu et al. in Mol. Syst. Des. Eng. 6:108–121, 2021;), and these molecules are attracting attention for their potential application in optoelectronic devices or medical materials (Shirota in J. Mater. Chem. 10:1–25, 2000;Nguyen in Surf. Coat. Technol. 206:742–752, 2011;Ostroverkhova in Chem. Rev. 116:13,279–13,412, 2016;Park et al. in Adv. Mater. 27:7583–7619, 2015; A. M. Grumezescu, Organic Materials as Smart Nanocarriers for Drug Delivery, Elsevier (2018);Zhang et al. in Chem. Soc. Rev. 48:5564–5595, 2019;). Such stimuli-responsive molecules change their properties in response to changes in physical stimuli such as heat, light, and electric potential, or to a change in the chemical environment such as in pH or concentration.