Since soon after the discovery of radio pulsars in 1968, their scintillation due to multi-path scattering in the interstellar medium (ISM) emerged as a useful tool in studying the ISM. For example, a recent study with the Five-hundred-metre Aperture Spherical Telescope (FAST) by Yao et al. [1] has demonstrated scattering due to a 100K-year-old supernova remnant (the Monogem Ring) as well as close alignment of the pulsar spin axis and its velocity vector. Ocker and collaborators [2], also using FAST, unveiled a plethora of structures-bow shocks, interstellar bubbles, and sheets-in scattering toward 8 pulsars and extracted useful information about plasma turbulence in those structures. Other successes include the precision determination of binary pulsar orbital inclinations and the detection of a scintillation arc toward a Fast Radio Burst Repeater [3], again utilizing FAST's remarkable sensitivity. Much of the recent progress stems from scintillation arc studies, a technique that was introduced in 2001 (see previous references for details), but that has been honed into a high-precision tool in the last five years. Now, we have a definitive detection of scattering by the million-year-old supernova remnant the Gum Nebula [4]. Although this structure, which extends nearly 40 • across the southern sky, had been proposed as a scattering screen for background pulsars, it took two years of meticulous dualfrequency observations with the 65-m diameter Tian Ma Radio Telescope (TMRT) near Shanghai to demonstrate this conclusively. Central to this achievement was the simultaneous observation at two radio frequencies (2.25 and 8.30 GHz) that are relatively high frequencies for pulsar observations. *Corresponding author (email: dan.stinebring@oberlin.edu) Since radio wave scattering decreases rapidly with observing frequency (bending angle ∝ ν -2 ) the high frequencies employed in this study allowed a scintillation arc to be seen along this relatively heavily scattered line of sight. Careful modeling of the behavior of the scintillation arc and other scintillation observables as the Earth orbits the Sun allowed the researchers to identify the front edge of the Gum Nebula as the main source of scattering for this pulsar. This pulsar was chosen because it is bright and definitely behind the nebula. However, there is no reason to believe that the sight line toward it is in any way special with respect to the Gum Nebula. Hence, the approximately two dozen known pulsars located behind the nebula can also be expected to have the nebula as a major source of scattering. Follow-up observations of these less bright pulsars will require larger telescopes such as FAST, MeerKAT, and the Square Kilometer Array (SKA), under construction in South Africa and Australia. Those results should yield details of Gum Nebula turbulence, discrete sub-structures, and, in some cases, physical conditions.