Wales has fallen silent to mark the 50th anniversary of the Aberfan disaster, which cost the lives of 116 schoolchildren.
A minute's silence was held across Aberfan and the rest of the country as people remembered the catastrophe, where 150,000 tonnes of coal waste slid down a hillside before smashing into a school.
Pantglas Junior School was buried by the coal rush on October 21, 1966, killing 116 children and 28 adults.
Prince Charles will also be in Aberfan to pay his respects at the Aberfan memorial garden.
He will visit a community centre, where he is expected to make a short speech, as well as meet survivors of and families linked to the disaster.
Described as Wales' darkest day, survivors will attend special memorial services near Aberfan across the day after the rest of the country joined them in observing a minute's silence at 9.15am.
ITV News Wales Correspondent Rupert Evelyn witnessed the anniversary tribute at the site where the school used to stand.
First Minister of Wales Carwyn Jones said the men, women and schoolchildren who lost their lives should never be forgotten.
"It is a truly heart-breaking moment in our history and no one who learns about the disaster can fail to be profoundly moved by it," he said.
"Half a century on, I hope the country as a whole will come together, with respect and compassion, to pause for a minute at 9.15am [today, Friday] and think of the community of Aberfan".
Services of remembrance will take place in a number of local churches as well as on the site of Pantglas school, which has now been turned into a memorial garden.
Survivor Jeff Edwards said the events of the day had affected him and his fellow classmates all their lives.
For two hours the eight-year-old was pinned next to a dead girl from his class, with her head next to his face.
What we've all experienced are classic symptoms of post-traumatic stress disorder. There's no doubt it has affected me on a daily basis. I still have nightmares and sometimes suffer from deep bouts of depression.
The tragedy was all the more bitter to deal with given that coal bosses had been warned about "flowslides" prior to the disaster.
Despite a 76-day public inquiry, no-one ever faced prosecution or lost their job.
A protracted row about removing other coal tips forced frustrated locals to take £150,000 out of a memorial fund to pay for the clean-up bill.
The money was eventually returned, but only after decades of campaigning.