A graphic real-time re-enactment of Britain's worst mining tragedy has brought the agony of the day's events to life on Twitter.
The Senghenydd colliery disaster was caused by an underground gas explosion in a sprawling mine employing more than 2,500 people near Caerphilly.
The tweeting began with the miners' journeys to work and continued through as the day's events unfolded:
The sound of a terrific explosion echoes down the Aber Valley
In the pit yard workmen are making stretchers & litters for the injured while undertakers draw on stocks of coffins for those beyond help
The inspectors recommend the hot debris from the falls & fire is removed to the surface in trams. Work starts on this immediately
The thousands who have died in Welsh mining accidents over the years were remembered today on the anniversary of the worst mining disaster in the UK.
On 14th October 1913, an explosion in Senghenydd near Caerphilly killed 439 miners and one rescuer.
ITV News Wales correspondent Dan Rivers reports:
A memorial to all of the victims of Wales' mining disasters will be unveiled today, 100 years to the day since the Senghenydd Colliery Disaster.
439 miners, and one rescue worker, were killed at the Universal Colliery in Senghenydd on 14 October 1913.
The Wales National Mining Memorial and Gardens will be unveiled in Senghenydd at lunchtime.
It features a path, with tiles each dedicated to the 198 mining disasters that have happened across Wales.
More than 5,000 people have died in those disaster over the last 250 years; more than 1,000 in the last 100 years.
There is also a tile acknowledging the lives lost in other mining explosions and tragedies, and mining-related illness.
This tile includes a reference to the four victims of the Gleision disaster, in 2011, with the hope that it will be the last such tragedy.
A wall of remembrance will also mention all of the men who died at the two Senghenydd disasters, in 1913 and 1901.
The day of commemoration will begin with the sounding of the original Universal Colliery pit hooter, which will ring out down the Aber Valley at 8.10am, as it did 100 years ago.
It will end with evening tributes, including lantern parade and a memorial service.
Both Hilary Barbrook's grandfathers were killed in the explosion at the Universal Colliery in Senghenydd on 14 October 1913.