Almost a century after they fell, the victims of Australia's biggest wartime catastrophe have risen from the dark anonymity of a mass grave. Since 2010 their names - or some, at least, of the thousands of casualties - have proudly shone on white headstones in the neighbouring cemetery.

And now next door their stories, photos - even mugs and toothbrushes - will illuminate their lives and commemorate their sacrifice.

Thomas Boucknooghe is the mediateur (it roughly translates as guide or intermediary) at the Musee de la Bataille de Fromelles.

He gave Fairfax Media a preview, filling in the still-blank shelves and half-finished displays with his vision of the museum - a resource for future generations.

He paused in front of a blank square where a video screen will show some of the thousands of casualties. ''It's really emotional,'' he said. ''You realise how important was this battle. In just 24 hours, how many people died on this battlefield.''

There are no signs yet on the walls, the video screens are silent, and artefacts returned to the battlefield from the Australian War Memorial sit in boxes, acclimatising to the French air.

The tour's arc starts in the shadows of an archaeological dig: explaining the intricate work by many experts that turned scraps of 90-year-old DNA from 250 bodies in the grave at Pheasant Wood into 126 names for the tombstones in the cemetery.

The museum will display some of the 6000 artefacts recovered from the land - clothing, badges, even a small toothbrush carved with the name of its owner.

''There were not a lot of personal items on them,'' Mr Boucknooghe says. ''Maybe [the toothbrush was engraved] because they didn't want to lose it or maybe it was just because they wanted to have, to keep the feeling of having something for yourself.''

The museum then displays trenches of another kind - opposing re-creations of the Germans' ordered and reinforced bunkers and sappers' tunnels that may have housed a young Adolf Hitler, versus the iron-and-sandbag improvisations of the Australian and British troops down the hill.

It's not just a model: it incorporates wood and steel from the original fortifications, recovered by a local organisation Fromelles et Weppes Terre de Memoire.

Screens will show postcards from German soldiers and letters from Australians (''good luck to read it, the writing is really different'', Mr Boucknooghe says).

The key point of the exhibition is a circular room where an animated, projected map will show the ebb and flow of the battle, the movement of the troops as the Australians charged through machinegun crossfire to claim German positions that they could not hold as the counter-attack enveloped them.

Surrounding walls will hold uniforms and equipment of the armies and items such as shells, guns, shrapnel helmets and backpacks.

Three video screens will remember the 8500 casualties - the dead, the wounded and the prisoners.

''The purpose is not to shock people. It's not a bloodbath we want to show. It's something strong enough to make me feel how impressive was this battle for the survivors.''

Finally, there is a display of 21 portraits and personal stories of some of the fallen. ''It was not supposed to be their fight,'' Mr Boucknooghe said. ''This site is supposed to tell you why they did it.''

In 24 hours in July, 1916, Australia lost more soldiers than in the Boer War, Korean War and Vietnam put together.

Many of the dead lay in an unmarked mass grave, until a scientific project matched DNA to names and led in 2010 to the new Fromelles cemetery.

The museum hoped to open on April 23, but was delayed by the need to re-do some of the graphics and text, and to muffle a noisy airconditioning system.

It will now open at the end of June, about the same time as - possibly the last set of - new names are carved into the headstones outside.