Scientists say they believe they have captured the elusive Higgs Boson particle that gives matter mass.
Professor John Womersley, chief executive of the Science and Technology Facilities Council, told reporters at a London briefing that they had discovered a particle consistent with the Higgs Boson.
Discovery is the important word. That is confirmed. It's a momentous day for science.
There is a strong Welsh connection to the groundbreaking scientific project as Dr Lyn Evans from Aberdare was the project leader.
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It's certainly not the brightest of starts to the day, with drizzly rain in places.
It will feel much milder tonight that it did last night, with patchy showers around the coasts.
Well what a difference a day makes! It's the calm after the storm today!