For questions that require imaging reside
cells for multiplied time intervals deep inside
tissues, two-photon microscopy is the current
approach of alternative.
Like confocal microscopy, two-photon microscopy
uses a laser to excite a fluorescent tag within
a pattern and detectors to measure the emitted
gentle.
Nonetheless, unlike the lasers used for confocal
microscopy, which provide single-photon excitation,
the lasers utilized in two-photon microscopy
excite by way of using near simultaneous absorption
of two long wavelength (~800 nm) photons.
This results in several targeted benefits.
The long wavelengths used for two-photon microscopy
are much less detrimental and penetrate extra
deeply into tissues than these utilized in
confocal microscopy.
Moreover, the requirement for close simultaneous
absorption of 
two photons signifies that excitation is most
effective achieved close 
the focal plane the place the laser light
is most focused.
This has 
two particular advantages.
One is that there is little tissue injury
to the regions above and beneath the focal
aircraft that are not being imaged.
Additionally, there's no out-of-focal point
mild that would make 
the snapshot blurry and tricky 
to interpret.
Two photon microscopy, two photon microscope,
two photon imaging, two photon absorption,
multiphoton microscopy
