two-photon microscopy

A laser microscope that can image living tissue up to a fraction of a millimetre below the surface with little damage. It works by making fluorescent markers glow only at the exact point where the laser is focused, which keeps the image sharp at depth.

In neuroscience it is used to watch individual neurons at work, almost always in laboratory animals fitted with a small window in the skull. It needs the animal to stay under the microscope, which limits how long and how freely it can be observed.

Documented real-world example: in the UC San Diego study behind transparent brain-computer interfaces, a two-photon microscope imaged neurons up to 250 micrometres deep, shining its laser through the transparent graphene array.

Related terms: calcium imaging, transparent brain-computer interfaces, graphene

Sources: Two-photon excitation microscopy — Wikipedia; Transparent Brain-Computer Interface Uses AI and Nanotech — Psychology Today (Cami Rosso, 24 Jan 2024)