After synthesizing AIE-Tz, we investigated their emission properties in dilute solutions in DMSO and aggregates in water. Not surprisingly, both AIE-Tzs and PR-Tz only exhibited very weak emissions in dilute solutions (quantum yield < 0.002, shown in Table , Supporting Information). This could be due to two reasons: firstly, AIEgens do not show strong emission in solution because of their molecular motions, and secondly, the tetrazine unit acts as a quenching unit. However, we still observed non-negligible emissions from AIEgens or Pyrene moieties that could cause background emission problems during fluorescence imaging. By changing the water fraction, molecular aggregation was observed with dynamic laser scattering measurements (Figure , Supporting Information). Interestingly, not only does PR-Tz, whose fluorophore is impacted by the aggregationcaused quenching effect, show further quenched emission upon molecular aggregation, but also AIE-Tzs, which are expected to exhibit enhanced emission, demonstrate further suppressed emission under the same conditions (Figure ), apart from the negligible emissions from the tetrazine moiety peaked at around 600 nm (Figure , Supporting Information). Specifically, TPE-Tz exhibited very weak emission at 470 nm coming from tetraphenyl ethylene core , and this emission's intensity decreased upon aggregation (Figure ). TPA-based tetrazine molecules displayed slightly stronger emission than TPE-Tz in dilute solution, and the emission was well quenched upon water addition (Figure ). This more notable emission of TPA tetrazine adducts over TPE-Tz could be a consequence of the less flexible structure of TPA units compared to TPE units. Indeed, PR-Tz, which has the most rigid structure, showed the strongest emission among all tetrazine compounds in DMSO, and a significant emission decrease was observed upon water addition (Figure ). This phenomenon of AIE-Tz suppressing its emission upon aggregation effectively highlights tetrazine's potential to reduce the background signals from fluorogenic dyes, thereby contributing to ultrahigh fluorescence turn-on ratios in the aggregate state. This intriguing observation further spurred our interest to explore this quenching effect more thoroughly.