JWST MIRI-MRS spectrum of the Class I TMC1-W source showing a forest of hot H₂O water lines. A LTE slab model at 1200 K is included for comparison in blue. The Spitzer-IRS spectrum of the binary TMC1 source is shown for comparison, illustrating that these types of detections were not possible prior to JWST. Figure adapted from van Gelder et al. (2024a), which shows the model spectrum offset from the data.