What is a dye that highlights structures in a living tissue?

A common dye that highlights structures in living tissue is fluorescein. This fluorescent dye is often used in biological research and clinical applications, such as in ophthalmology to visualize blood vessels and assess ocular health. Fluorescein can bind to proteins and tissues, allowing for enhanced imaging under specific light conditions. Another example is DAPI, which selectively stains DNA in cell nuclei.