The new chamber is next to the Cardiff Bay office block the assembly has sat in since it was set up in 1999.
The building uses natural wood and slate and is designed with energy efficiency in mind.
Visitors will have unrestricted access to the upper floor on the main plinth level.
The building makes extensive use of natural materials such as wood and slate.
Finance Minister Sue Essex says the building 'raises the bar... on environmental, public accessibility and design quality'.
This mirrored cone can be lowered to alter light levels in the chamber.
Dafydd Elis-Thomas in the chamber where he continues his duties as presiding officer.
First Minister Rhodri Morgan outside the front entrance on the day the building officially opened.
The view from the public chamber as AMs meet in the chamber for the first time.