(A) Linear density gradient (colour) leading to flux (arrows) with transverse component arising from $D_{\perp }$. (B, C) Diffusion coefficients $D_{\perp }$ and $D_{\parallel }$ as obtained from molecular dynamics simulation of a passive tracer particle in a chiral active bath of rotating dumbbells with density ρ_bath. The Péclet number Pe is proportional to a force applied to the dumbbell particles causing their rotation, such that a different sign of Pe amounts to an opposite rotation. The coefficients are numerically calculated in simulations with generalised Green-Kubo relations and the relation between flux and concentration by maintaining a constant density gradient (boundary flux). Reprinted with permission from [62]. Copyright©2021 the American Physical Society. (D) Comparison of two nearby particles subject to normal (top) and odd (bottom) diffusion. Odd diffusivity circumvents the mutual steric hindrance of configuration space exploration and the particles mutually roll around each other. Reprinted with permission from [63]. Copyright©2022 the American Physical Society.