Amber has long been appreciated for its ability to preserve a moment in time as it encapsulated plant matter, bugs and other organisms. As a tool for ecosystem reconstruction, scientists have learnt a great deal. But recently researchers led by Ralf Tapper of the University of Innsbruck, have begun using amber and other fossil plant resins to reconstruct the composition of Earth’s atmosphere from the last 220 million years. The results suggest that atmospheric oxygen was considerably lower in the Earth’s geological past than previously assumed.