Why Can't Dyes Show a Thousand Proteins at Once?

Eric Betzig says a label with a truly narrow emission line would let a microscope watch a thousand proteins at once, because each spectrum would stay narrow. Fluorophores do not give that line. He puts the width at about 50 nanometers of emission spectra, and the excitation spectra are just as broad.

He still lets the bands overlap and then unmixes them. The lasers turn on and off for each one, and multiple cameras each watch one spectral band. He has also looked for help from plasmonics and little silver resonators. Nothing useful has come up. Delivery is a pain, the sample is no longer in a vacuum, and nearby electric fields cause stark shifts that perturb the lines.

He treats a caged ion in a buckyball, attached in a thousand different ways, as a later frontier. He says maybe that kind of work happens after he is dead and buried.