The company was founded in Århus in 1986 as Nielsen, Nielsen & Nielsen (later 3 X Nielsen) by Kim Herforth Nielsen, Lars Frank Nielsen og Hans Peter Svendler Nielsen. The latter left the company, which is today led by a partner group of three with Kim Herforth Nielsen as the Principal Architect.
In 2007 3XN established the research and development department GXN working on implementing new (green) materials and technologies in the studio’s projects. The R&D department also develops new projects and designs of lamps for instance. GXN is also behind the green Louisiana Pavilion displayed at the Danish art museum Louisiana during COP15. The pavilion is built with a biocomposite especially developed for the purpose. GXN works with Cradle to Cradle Denmark at developing the first Danish building manual based on the Cradle to Cradle principles.