A new atomic clock has extended from one dimension to three, becoming the most precise timekeeper in existence - just 3.5 parts error in 10 quintillion (that's 1 followed by 19 zeroes) in two hours.
The clock was built by JILA, a collaboration between the University of Colorado and the National Institute of Standards and Technology, which also built the world's previous record holder for the most precise clock in 2015.
It had a precision of 2 parts error in 1 quintillion (18 zeroes), and could keep time without losing or gaining a second for 15 billion years - longer than the age of the universe.
"We are entering a really exciting time when we can quantum engineer a state of matter for a particular measurement purpose," said NIST physicist Jun Ye.
The 2015 atomic clock was based on a one-dimensional lattice of strontium atoms, held in place by laser beams.