A noticeably large number of entrants for the 2019 Innovation Award are working on solutions for two-photon/multi-photon microscopy. But what is this actually?
If two or three photons encounter a fluorescence molecule simultaneously, they combine their energy and strengthen the fluorescence signal exponentially. On the one hand, this increases how deep researchers can look into tissue (to 1 mm). On the other hand, thanks to the potential energy from the simultaneously arriving photons, lower energy, long-wave laser light can be used instead of tissue-damaging UV lasers. This makes the process interesting for investigating living cells and slows down the bleaching of fluorescent dyes.