Biological (A–E) and synthetic (F–J) chiral active matter over several length scales. (A) The chemical potential difference for protons across the membrane in the biological rotary machine ATP synthase (diameter σ≈10 nm) is converted into chemical energy of ATP synthesis causing a rotation. Reprinted with permission from [29]. Copyright©2001 The Author(s). (B) Marine algae Effrenium voratum (σ≈10 m) with superimposed trajectory showing chiral circular swimming behaviour at the air-liquid interface. Reprinted with permission from [30]. Copyright©2021 National Academy of Sciences. (C) Bacteria Thiovulum majus (σ≈10 m) on a surface induce a chiral tornado-like flow that leads to an attraction and mutual orbital rotation of neighbouring cells. Reprinted with permission from [31]. Copyright©2015 American Physical Society. (D) Actively spinning starfish embryos (σ≈200 m) form a co-rotating pair by flow generated by each other. Reprinted with permission from [32]. Copyright©2022 Springer Nature. (E) Volvox colonies (σ≈500 m) have a ciliated surface of beating flagella pairs on each somatic cell (small dots), leading to directed motion and chiral rotation. Reprinted with permission from [33]. Copyright©2009 the American Physical Society. (F) Silica rod-like colloids (σ≈1 m) with an adhered magnetic tip perpendicular to the symmetry axis [42] orient perpendicular to the substrate and rotate in sync with an externally applied rotating magnetic field. The colloids excite a rotational flow field advecting nearby colloids. Shown streamlines are obtained from simulations. Reprinted with permission from [34]. Copyright©2023 The Author(s). (G) Chiral magnetic colloidal spinners (σ≈2 m) drag the surrounding fluid and exert hydrodynamic transverse and magnetic attractive forces. Upper image and lower image are reprinted with permission from [43, 35], respectively. Copyright©2019 and 2022 Springer Nature. (H) Vaterite colloidal particles (σ≈2-12 m) asynchronously rotate in circularly polarised light resulting from birefringence, leading to hydrodynamic spin-orbit coupling. Reprinted with permission from [39]. Copyright©2023 The Author(s). (I) 3D-printed granular gear-like rotors (D1=16 mm, D2=21 mm) with tilted bristles at the bottom can be brought into a state of active rotation powered by vertical vibration. Reprinted with permission from [40]. Copyright©2020 National Academy of Sciences. (J) Two oppositely arranged Hexbug robots mounted on a foam disk (σ≈5 cm) constitute a rotor on the centimeter scale. Reprinted with permission from [41]. Copyright©2020 the American Physical Society.