This artist’s impression shows how photons in the cosmic microwave background (CMB) are deflected by the gravitational lensing effect of massive cosmic structures as they travel across the universe. Gravitational lensing creates tiny, additional distortions to the mottled pattern of the CMB temperature fluctuations. A small fraction of the CMB is polarized; one component of this polarized light, B-modes, have been given an additional signature by gravitational lensing.