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Physicists have succeeded in chilling molecules to the coldest temperature ever reported.

The experiment lowered the temperature of selected molecules to 2.5 thousands of a degree above absolute zero.

And the result could prompt new research in areas ranging from quantum chemistry to tests of the most basic theories in particle physics.

Scientists at Yale University have created the world's coldest molecules. Based in Connecticut the experiment chilled them to almost absolute zero. It is the coldest temperature ever recorded for any molecule. Pictured here is an optical cavity used to precisely fine-tune lasers that then trapped and cooled the molecules

The research, published in the journal Nature, was conducted by scientists at Yale University in Connecticut.

It involved dropping the temperature of strontium monofluoride with lasers in a process known as magneto-optical trapping (MOT).

At almost absolute zero (-273.15°C or -459.67°) they are the coldest molecules ever achieved through direct cooling, representing a physics milestone.

'We can start studying chemical reactions that are happening at very near to absolute zero,' said Dr Dave DeMille, a Yale physics professor and principal investigator.

'We have a chance to learn about fundamental chemical mechanisms.'

Magneto-optical trapping has become very popular with atomic physicists in the past generation - but only at the single-atom level.

This experiment marks the coldest recorded temperature for molecules, which are groups of two or more atoms.

The technology uses lasers to simultaneously cool particles and hold them in place.

'Imagine having a shallow bowl with a little molasses in it,' Dr DeMille explained. 

'If you roll some balls into the bowl, they will slow down and accumulate at the bottom.

'For our experiment, the molecules are like the balls and the bowl with molasses is created via laser beams and magnetic fields.'

The results could prompt new research into areas such as quantum chemistry. Magneto-optical trapping has become very popular with atomic physicists in the past generation - but only at the single-atom level. This marks the coldest recorded temperature for molecules (illustration shown), groups of two or more atoms

Magneto-optical trapping involves holding molecules in place with lasers. In so doing the physicists were able to cool the molecules to a fraction of a degree above aboslute zero (artist's illustration shown)

Until now, the complicated vibrations and rotations of molecules proved too difficult for such trapping.

The Yale team's unique approach drew inspiration from a relatively obscure, 1990s research paper that described MOT-type results in a situation where the usual cooling and trapping conditions were not met.

Dr DeMille and his colleagues built their own apparatus in a basement lab. 

It is an elaborate, multi-level tangle of wires, computers, electrical components, tabletop mirrors and a cryogenic refrigeration unit. 

The process uses a dozen lasers, each controlled to extremely high precision.

'If you wanted to put a picture of something high-tech in the dictionary, this is what it might look like,' Dr DeMille said. 

'It's deeply orderly, but with a bit of chaos.'

The Yale team chose strontium monofluoride for its structural simplicity - it has effectively just one electron that orbits around the entire molecule. 

'We thought it would be best to start applying this technique with a simple diatomic molecule [those composed of only two atoms],' Dr DeMille said.

The discovery opens the door for further experimentation into everything from precision measurement and quantum simulation to ultracold chemistry and tests of the standard model of particle physics.