London's Natural History Museum has opened its £35m Darwin Centre, putting its 22m zoology specimens - the Spirit Collection - and research building on public view for the first time.

The new, eight storey building, designed by Guy Comely of HOK International, was funded entirely by the museum itself and is phase one of a project which will see a further building constructed to house the museum's entomology and botany specimens, taking the total project cost to around £95m. Fundraising for the second stage has begun and lottery money will fund part of the cost.

Temporarily linked to the rest of the museum by a bridge from the Waterhouse building's mammals gallery, the Darwin Centre consists of specimen storage, offices and laboratories, all of which are on view to the public on hourly tours.

Smaller specimens are displayed in cabinets in temperature controlled rooms while the larger are in tanks in the basement.

In the atrium, visitors can access a vast information bank via the museum's intranet, as well as take part in live debates or forums with research teams around the world via state of the art audio-visual equipment in a 150-capacity conference area.

Guy Comely's design uses terracotta bricks to match the Natural History Museum's hand-fired exterior. It also has an inflatable lightweight roof, like that used for the Eden Project, which lets light flood in as well as making the building thermally efficient. All-glass solar walls track the movement of the sun.

Phase two, designed by CF Møller and expected to get underway in 18 months time, will sit between the Waterhouse building and Darwin Centre, permanently linking the two. The buildings will provide three sides to landscaped grounds forming an outdoor 'auditorium'. The whole project is due for completion in 2007.

'The Darwin Centre is aimed at slightly older children,' said director, Sir Neil Chalmers. 'It's a working scientific building and is also like a library; visitors can research their own interests as well as seeing scientists at work.' Details: www.nhm.ac.uk/darwincentre