A light-driven molecular rotor was developed by researchers at the University of Groningen, including N. Koumura, R.W.J. Zijlstra, R.A. van Delden, N. Harada, and B.L. Feringa. Published in *Nature* (1999), the study describes a chiral, helical alkene that undergoes monodirectional rotation when exposed to light. The rotor consists of a central carbon-carbon double bond with two chiral centers, and its rotation is driven by ultraviolet light or temperature changes. The rotation involves four discrete isomerization steps, with each 360° rotation being unidirectional due to the axial chirality and the presence of two chiral centers. The study demonstrates that the molecular rotor can convert energy into unidirectional rotary motion, a feat previously difficult to achieve. The rotor's structure was confirmed through spectroscopic methods, including NMR and CD spectroscopy, and the results show that the molecular rotor can rotate in a clockwise direction when exposed to light. The study also highlights the importance of axial chirality and the two chiral centers in the observed monodirectional behavior. The findings suggest that chiral alkenes based on this system may be useful as basic components for 'molecular machinery' driven by light. The research provides insights into the design and function of molecular motors, which are common in biological systems. The study also discusses the broader implications of the findings for the development of molecular machines and the understanding of molecular motors in biological systems.A light-driven molecular rotor was developed by researchers at the University of Groningen, including N. Koumura, R.W.J. Zijlstra, R.A. van Delden, N. Harada, and B.L. Feringa. Published in *Nature* (1999), the study describes a chiral, helical alkene that undergoes monodirectional rotation when exposed to light. The rotor consists of a central carbon-carbon double bond with two chiral centers, and its rotation is driven by ultraviolet light or temperature changes. The rotation involves four discrete isomerization steps, with each 360° rotation being unidirectional due to the axial chirality and the presence of two chiral centers. The study demonstrates that the molecular rotor can convert energy into unidirectional rotary motion, a feat previously difficult to achieve. The rotor's structure was confirmed through spectroscopic methods, including NMR and CD spectroscopy, and the results show that the molecular rotor can rotate in a clockwise direction when exposed to light. The study also highlights the importance of axial chirality and the two chiral centers in the observed monodirectional behavior. The findings suggest that chiral alkenes based on this system may be useful as basic components for 'molecular machinery' driven by light. The research provides insights into the design and function of molecular motors, which are common in biological systems. The study also discusses the broader implications of the findings for the development of molecular machines and the understanding of molecular motors in biological systems.