Beneath a mountain, an experiment is about to begin that could prove the existence of some of the strangest particles known to science.
Physicists are hoping to find the first evidence of dark matter – a hidden substance that is thought to pervade the Earth and the Universe.
BBC World Service science reporter Rebecca Morelle has been to Italy to take a look inside the Darkside-50 experiment at the Gran Sasso National Laboratory before it is switched on.
Use the link above to access a three minute video that gives you an inside look at the Gran Sasso National Laboratory and the Darkside-50 experiment, an experiment searching for dark matter.
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