Normal cellular processes in living organisms create biophotons, although the escaping light is not visible to us.
Many science fiction and fantasy stories feature characters that glow, such as ET's fingertip or demon markings in movies.
Scientists still aren’t sure whether these biophotons serve a purpose or if they’re just glowing motes of cellular junk.
According to Catalina Curceanu, a nuclear and quantum physicist, this phenomenon is not bioluminescence, but rather a different process.
This summary is part of our weekly scientific breakthroughs series, published every Thursday.
Author's summary: Living things produce tiny amounts of light.