NISP-S grism slitless spectroscopy mode. Left: NISP-P colour-composite image of the planetary nebula (PN) SMC-SMP-20 (Euclid Collaboration: Paterson et al. 2023), observed during the PV phase for wavelength calibration. The PN is located at the image centre; with a diameter of 0^′.^′40 it appears unresolved. Right: raw NISP-S 2D-spectrogram of the same area, the photometry field is sketched again with a green box. Each horizontal stripes is a spectrogram of a bright object. Small dots between these spectrograms are mostly cosmic rays hitting the detector. The PN can easily be identified in the 2D-spectrogram by the distinct emission lines above a weak continuum; it has been colourised for emphasis. The zoom below repeats the 2D-spectrum together with the extracted 1d-spectrum. Identified emission lines are marked. We note that the direction of the wavelength axis will differ on the sky depending on the specific grism used. The visible strong Paβ emission in YE -band and the Paα line in the HE -band lend a distinct purple colour to the PN and its prominent diffraction ring in the image on the left.