With the L-band 19-beam cooled receiver, FAST has a great sensitivity to uncover many details of the interstellar medium of the Milky Way. In the ingeniously designed project, the FAST Galactic Plane Pulsar Snapshot (GPPS) survey, spectral line data are simultaneously record when the key project is hunting for pulsars in the visible sky area of the Galactic plane of FAST within |b| ≤ 10°. Hong et al. processed the neutral hydrogen (HI) data in the sky area of 33° ≤ l ≤ 55° in the Galactic longitude and |b| ≤ 2° in the Galactic latitude, revealing the fine and clear structures of Galactic HI gas. The improvement in angular resolution and sensitivity over all previous surveys is impressive (see the News & Views by John M. Dickey). Hou et al. obtained the distribution of the ionized gas traced by Hnα radio recombination lines (RRLs) for the same sky area as the HI data, with a significantly better sensitivity than previous RRL surveys for uncovering the Galactic HII regions and the diffuse ionized gas of unknown origin (see the News & Views by Dana S. Balser). Xu et al. measured the Faraday effect of a large number of faint pulsars obtained by the GPPS survey, revealing the magnetic field structure in a much larger region in the Galactic halo and disk. Gao et al. scanned a sky area of 5° × 7° for radio synchrotron radiation and identified two new large and faint supernova remnants.