In standard ΛCDM, vorticity (swirling motions) in the large-scale matter flow is expected to be very small on linear and quasi-linear scales, with the cosmic web largely described by irrotational (curl-free) flows except in strongly non-linear cluster cores and shocks (Bernardeau et al. 2002; Pueblas & Scoccimarro 2009). Yet numerical simulations and observational analyses now indicate that significant vorticity and coherent spin can be associated with filaments themselves, with halo and galaxy spins aligned with filament vorticity and hints that entire filaments may rotate, suggesting surprisingly large-scale angular momentum generation that is not straightforwardly captured by simple ΛCDM tidal-torque expectations (Codis et al. 2015; Wang et al. 2021).