γ-Resorcyclic Acid-Based AIEgens for Illuminating Endoplasmic Reticulum**

Endoplasmic reticulum (ER) has emerged as one of the interesting sub-cellular organelles due to its role in myriads of biological phenomena. Subsequently, visualization of the structure-function and dynamics of ER remained a major challenge to understand its involvement in different diseased states including cancer. To illuminate the ER, herein we have designed and synthesized γ-resorcyclic acid-based small molecules, which showed remarkable aggregation-induced emission (AIE) property in water. This AIE property was originated from the dual intramolecular H-bonding leading to the self-assembled 2D aggregation confirmed by pH- and temperature-dependent fluorescence quenching studies as well as scanning electron microscopy. These small molecules illuminated the sub-cellular ER in HeLa cervical cancer cells as well as non-cancerous RPE-1 human retinal epithelial cells within 1 h. These novel small molecules have the potential to light up ER chemical biology in diseased states.