Ultra-photostable small-molecule dyes facilitate near-infrared biophotonics. Researchers have developed a series of aminofluorene (AF) dyes with molecular weights of 299–504 Da and spectra covering 700–1600 nm. These dyes exhibit high photostability, rapid renal clearance, and excellent cell permeability, making them ideal for in vivo imaging and sensing. The AF dyes are based on a ground-state antiaromatic structure, which allows for a narrow HOMO-LUMO gap and strong vibronic coupling, resulting in ultrafast excited-state dynamics and exceptional photostability. The dyes show promising applications in multispectral fluorescence and optoacoustic imaging, as well as in detecting reactive oxygen species (ROS) and other biological markers. The study highlights the potential of antiaromaticity as a useful design rule for dye development, enabling performance essential for modern biophotonics. The AF dyes also demonstrate the ability to be functionalized for tunable pharmacokinetics and biodistribution, making them powerful tools for in vivo near-infrared bioimaging and sensing. The results support the argument for ground-state antiaromaticity as a useful design rule of dye development, enabling performances essential for modern biophotonics.Ultra-photostable small-molecule dyes facilitate near-infrared biophotonics. Researchers have developed a series of aminofluorene (AF) dyes with molecular weights of 299–504 Da and spectra covering 700–1600 nm. These dyes exhibit high photostability, rapid renal clearance, and excellent cell permeability, making them ideal for in vivo imaging and sensing. The AF dyes are based on a ground-state antiaromatic structure, which allows for a narrow HOMO-LUMO gap and strong vibronic coupling, resulting in ultrafast excited-state dynamics and exceptional photostability. The dyes show promising applications in multispectral fluorescence and optoacoustic imaging, as well as in detecting reactive oxygen species (ROS) and other biological markers. The study highlights the potential of antiaromaticity as a useful design rule for dye development, enabling performance essential for modern biophotonics. The AF dyes also demonstrate the ability to be functionalized for tunable pharmacokinetics and biodistribution, making them powerful tools for in vivo near-infrared bioimaging and sensing. The results support the argument for ground-state antiaromaticity as a useful design rule of dye development, enabling performances essential for modern biophotonics.