Researchers at London’s Natural History Museum will work in the public eye alongside 20m specimens

One of the most startling additions to any British museum, the £78m Cocoon at the Natural History Museum at South Kensington in London, an enigmatic, blobby form eight storeys high and 65m long in a giant glass box, will open to the public on September 15.

The structure has been created to shelter over 20m specimens of plants and animals, as well as laboratories for 220 scientists. This will be the first time that the museum’s scientists as well as its specimens will be on display.

Booking is now open for free tickets for 2,500 places on public tours every day.

Among the 17m insect and 3m plant specimens, there will be many items collected in recent years by staff on plant safaris, and others brought back over 150 years ago by Charles Darwin and Alfred Russel Wallace, the 19th century scientist whose parallel work on natural selection finally shocked Darwin into publication.

A collection of plants gathered by Sir Hans Sloane, whose work formed the basis of both the British and the natural history museums, will be on show, as well as a specimen of the famous “vegetable lamb of Tartary” – a type of fern whose cottony growth sparked the cherished legend of a plant that bore real living lambs as fruit.

Phone bookings are now being accepted for the tours, on 020-7942 5725, and online booking will open from mid-August.