Whilst the invisible effect lasted for only an extremely brief period -- an estimated 40 femtoseconds -- it demonstrates that such an exotic state of matter can be created using very high power X-ray sources.

'What we have created is a completely new state of matter nobody has seen before,' said Justin Wark, physics professor at the Oxford University and a study co-author.

'Transparent aluminium is just the start. The physical properties of the matter we are creating are relevant to the conditions inside large planets,' said Wark.

'We also hope that by studying it we can gain a greater understanding of what is going on during the creation of 'miniature stars' created by high-power laser implosions, which may one day allow the power of nuclear fusion to be harnessed here on Earth,' he added.

Wark added: 'What is particularly remarkable about our experiment is that we have turned ordinary aluminium into this exotic new material in a single step by using this very powerful laser.'

These findings were reported in Nature Physics.