Scientists believe they've found the oldest relics of life on Earth - tiny 3.4-BILLION-YEAR-OLD fossils in Western Australia.
The remains of microscopic bacteria, discovered in sandstone rock, have been studied using special techniques.
It's shown these miniscule lifeforms - so small you can't see them - lived on a chemical called sulphur, not oxygen.
On ancient Earth, oxygen wasn't widely available, so life had to find other ways to survive.
"Such bacteria are still common today," explained Professor Martin Brasier of Oxford University.
"Sulphur bacteria are found in smelly ditches, soil, hot springs... anywhere where there's little free oxygen."
Experts are keen to trace these early microscopic forms of life, because it may help with the hunt for life elsewhere in our Solar System.