DiI (DiIC18(3)) is a lipophilic membrane dye commonly used as a long-term tracer for neurons and other cells. DiI fluoresces very weakly before it enters the cell membrane, and only after it enters the cell membrane can it be excited to emit a strong orange-red fluorescence (λex=549 nm, λem=565 nm).
ICG-OSu, also known as ICG NHS ester, is a near-infrared fluorescent agent commonly utilized for the development of in vivo imaging probes due to its amine-reactive properties.