The concept of stopping light in its tracks is one that has long captured the imagination of scientists. Now, Tamar Goldzak and co-workers from Brazil and Israel have theoretically demonstrated that the group velocity of light can tend to zero in parity–time (PT)-symmetric systems. They show that zero group velocity may be achieved if a waveguide system is prepared at an exceptional point — a point where two optical modes coalesce with degenerate eigenfrequencies and eigenvectors. In their theory, they set up a system of a small waveguide array, coupling between a waveguide with gain and another with loss, to achieve a PT-symmetric system. The waveguide widths and distance between the waveguides are ~1 μm. In principle, the effect and structural parameters can be adjusted for optical pulses in a wide range of frequencies and bandwidths. The approach can potentially be extended to acoustic and other types of wave.