Detections of CCFs for Fe (SNR=5.8), CO (SNR=5.0), and V (SNR=4.7), and non-detection of H₂O (SNR<2.0) in the transmission spectrum of WASP-121b. Each squared panel shows the two-dimensional cross-correlation map in the velocity-velocity space (K_p − V_sys). The white dashed lines indicate the expected position of the planetary signal within the velocity-velocity space, namely the expected orbital (~216 km s⁻¹, Hoeijmakers et al. 2024) and systemic (3 8.35 ± 0.02 km s⁻¹, Delrez et al. 2016) velocities of WASP-121b. The rectangular panels on top depicts the one-dimensional cross-correlation of each species as signal-to-noise ratio versus systemic velocity. Detections of Fe and V are primarily driven by the optical HARPS observations, while the CO detection by the infrared CRIRES+ data (mostly K-band observations).