The company was founded in Aarhus, Denmark, in 1986 as Nielsen, Nielsen & Nielsen (later 3 X Nielsen) by Kim Herforth Nielsen, Hans Peter Svendler Nielsen and Lars Frank Nielsen. The firm quickly became known for creating buildings of substance with compelling aesthetics supported by a strong theoretical foundation. The international breakthrough came in the late 90s with the Danish Embassy in Berlin (1999) and the Muziekgebouw Concert Hall in Amsterdam (competition win in 1997).
Hans Peter Svendler Nielsen and Lars Frank Nielsen left the company in 1992 and 2001. Today, 3XN is led by a senior partner group of five with Kim Herforth Nielsen as the Creative Director.
In Denmark, 3XN is known for such projects as Ørestad Gymnasium (2007), the renovation of Tivoli’s Concert Hall (2005), Alsion, university, concert hall and research centre in Sønderborg (2007), Hotel Bella Sky (2011), UN City (2013), Denmark’s National Aquarium, The Blue Planet (2013), Royal Arena (2017) and Lighthouse in Aarhus (2022).
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.
In 2010 3XN created the exhibition Mind Your Behaviour, which was shown at Danish Architecture Centre and at Aedes Gallery in Berlin.
^"Nykredit Architecture Prize". Nykredit website (in Danish). Copenhagen, Denmark: Nykredit Holding A/S. 2013. Archived from the original on 27 March 2014. Retrieved 30 November 2013.