water‐soluble fluorescentbioimaging dyes by introducing the imidazolium‐based ionicliquid (IL) pendants into a fluorescent skeleton. A new type of water‐soluble imidazolium‐anchored squaraine dye was synthesized accordingly. The relationship between the aggregate of squaraines and their fluorescent cell imaging application was elucidated in detail. Firstly, the aggregationbehavior of squaraines in water