There was a buzz around Bankside this morning as Tate Modern's Herzog & de Meuron extension opened its doors to press, en masse. At the top of the grandiose, central concrete staircase, we find the new Tate store, double height and stretching to an impressive 500 sq m. George Gottl of the Netherlands-based consumer experience agency UXUS walked Wallpaper* around.

'We've thought about every detail,' he explains. 'From the women's accessory displays, to the bespoke bookshelves to the t-shirt mannequins.' With such a broad range of items in stock, creating a fluid and unifying shop floor was essential. 'Every unit you see here is on wheels,' Gottl adds, pushing a towering display cabinet, attached to an exposed, industrial runner. 'So, as the exhibitions and needs of the museum change, the store can be continually adjusted to fit. I think of it like a marketplace, with stalls that can be completely dismantled and reconfigured, depending on the product they're selling.'

Even the lighting is 'permanently temporary' – it moves with the shelves. Discreet LED strips are embedded into the framework of the modular units, shining a spotlight on each item. 'When the strip lights are switched off, it's amazing how different the space looks,' Gottl notes. 'But when they're on, the store feels more like an extension of the gallery space, giving each object an even more premium feel – so the customer might be pleasantly surprised by the price tag.'

The store stocks similar items to the existing River shop (postcards, mugs, art supplies) but there is a heightened focus on limited edition art books and prints, which occupy a library-sized shelving unit across the back wall.

Splashes of colour come courtesy of the dedicated children's area, which benefits from padded, child-sized cubbyholes carved directly into the bookshelf – perfect resting places for kids, after a long tour of the now gargantuan museum. Elsewhere, things feel rather more grown-up, with powder-coated steel fixings, Tate-typical concrete floors and accents of darkened wood.

The excitement of the opening day is infectious, and Gottl's passion for the project is clear. 'Working closely with Tate Modern's enterprise team, we realised the importance of the store in generating income for the not-for-profit gallery,' he concludes. 'We have always admired Tate for its visionary approach – it has been an enormous honour to be part of the team that is making that vision a reality.'