Compared with Gram staining, fluorescence imaging is considered to be more sensitive and convenient for detection and differentiation . To date, AIE biomaterials have been widely utilized for bacterial imaging based on strategies summarized as follows. The most universal strategy is to introduce positive charges into AIE biomaterials to bind the bacterial envelope through electrostatic interaction , since the lipopolysaccharides (LPS), teichoic acid and peptidoglycan in the bacterial cell wall were all reported to be negatively charged . Michelle et al. designed an AIE probe of TTVP with two positive charges (Fig. ) . TTVP could selectively target Gram-positive bacteria S. aureus through a washing-free procedure with only 3 s of incubation period, implying its ultrafast bacterial discrimination feature. Furthermore, a receptor-targeting labeling strategy is introduced since various receptors exist on the bacterial envelope . developed a receptor-targeting AIE PS (CE-TPA) by conjugating cephalothin (a β-lactam antibiotic) with a cationic AIE probe and the probe could target penicillin-binding proteins (PBPs), which is the main target of β-lactam antibiotics (Fig. ) . As a result, CE-TPA could target Grampositive methicillin-resistant Staphylococcus aureus (MRSA). However, the probe failed to stain ampicillin-resistant Escherichia coli (Amp r E. coli) due to the denser cell wall of Gram-negative bacteria. To achieve more stable and durable labeling, covalent labeling strategies like clickable and metabolic strategies have been developed in recent years . An AIE probe modified with isothiocyanate (NCS), CDPP-NCS, was utilized for covalent labeling through click reaction between NCS groups and amino groups (Fig. ) . It is notable that the probe could stably retain on the envelope for over 48 h without leakage, enabling the monitoring of interaction between bacterium and macrophage, which benefits the study the infection process. In addition, metabolic strategies can be applied as well. . D-alanine (D-Ala) could be selectively utilized by bacteria for its significant role in the synthesis of peptidoglycan. A bacteria-metabolizable AIE probe TPEPy-D-Ala that consists of D-alanine and AIE fluorophore was thus developed for fluorescence turn-on imaging of intracellular bacteria in living host cells (Fig. ). Notably, the septal planes of bacteria showed stronger signals owing to the ongoing peptidoglycan synthesis (the white arrows in Fig. ).