Long-term behavior of GRS 1915+105 monitored by MAXI and NICER. Top panel: Daily flux measured by MAXI in the 2−20 keV band. The duration of NICER and Insight–HXMT observations is shown at the top with cyan and dark orange stripes. The dotted black lines denote the available quasi-simultaneous observations by two instruments. Middle panel: Intensity of GRS 1915+105, defined by the raw photon count rate registered in the 1−10 keV band of NICER. The spectral states are classified with spectral-timing features and denoted with arrows. More details can be found in the literature. Bottom panel: Hardness of the spectra, defined by the raw count rate between the 5−10 keV band and the 1−5 keV band of NICER. The vertical dash-dotted magenta line (∼MJD 58593) represents the start point of the pre-flare dip, and the dash-dotted green line (∼MJD 58617) marks the passing of this source into the obscured state.