People across Wales are switching off their lights for an hour this evening and lighting a candle of remembrance.
ITV Wales correspondent Richard Morgan writes about his experience of researching the stories behind those killed in the Great War
All in one place: See some of ITV Wales's reports marking the centenary of the outbreak of the First World War here.
A special poppy-shaped garden has been created in Caerphilly to remember those who fought in the First World War. The garden will contain poppies and various other flowers.
It will be officially unveiled today and the garden will serve as a reminder of the centenary of the outbreak of World War One.
Portraits of servicemen from north Wales who died during the First World War are being projected on to the side of Pontio Arts Centre in Bangor tonight.
The images are being beamed from Bangor's Memorial Arch on to the arts centre to mark the connection between the sacrifices of the past and the hopes of the future.
It's part of a memorial service marking the outbreak of the Great War.
Lights are being turned out across Wales this evening in an event marking one hundred years since Britain entered World War One.
A candlelit vigil is taking place at Llandaff Cathedral, with a service led by Archbishop of Wales Dr Barry Morgan. First Minister Carwyn Jones and the Duke and Duchess of Gloucester are amongst those attending.
People are being encouraged to switch out their lights between 10pm and 11pm and light a candle in remembrance for those who lost their lives in the Great War.
The declaration of war this day a century ago changed just about every life across Wales. It transformed David Lloyd George - from politician to statesman . He was - by 1918 - described as 'the man who won the war' - the Prime Minister and the most famous person in Britain. All this from a man who started life in a small cottage on the Lleyn peninsula: Rob Shelley has been looking at the life - and legacy - of Lloyd George.
Landmarks across Wales will turn out their lights tonight as the UK marks the centenary of the outbreak of the First World War.
Between 10pm and 11pm the lights will be extinguished leaving just a single light or candle burning for a shared moment of reflection.
– Cllr Phil Bale, Cardiff City Council leader
It is right that we commemorate and remember those who took part in the First World War in this centenary year and always. The bravery and sacrifice of those who fought and of the communities on the home front, continues to humble all of us.
Jonathan Hill has been at Mametz Wood on the Somme because there is no better symbol of the appalling lost of life and of bravery shown by ordinary Welsh soldiers than this Dragon. It looks out across fields that lead to a small wood where four thousand Welshmen were killed or wounded in just a couple of days. Jon has been finding out about what happened there and investigating the stories of some of the men who gave their lives to capture the wood.
Many of the tales of those who fought in the Great War are still being used to educate the children of today. Andrea Byrne reports.
Members of Gwent police have marked a moment of silence as Wales remembers those who fought in the First World War.
One of the main commemorations of the day will take place in Mons this evening, the place where the first and last soldiers of World War One died. David Wood has been speaking to the family of one man from Pembrokeshire whose body is buried there