TESS light curve of WASP-121b. Upper panels: photometric data (blue points) phase-folded at the orbital period of the planet. The lower sub-panel zooms in on the planetary phase curve, clearly visible in the binned exposures (black points). Our best-fit model to the complete light curve is plotted as a solid red line. The corresponding temperature distribution of the planet is shown at regular phase intervals. The flux is normalized to unity during the secondary eclipse, when the stellar light alone is measured. Lower panels: residuals between the photometric data and the best fit.