The node was initially installed on the station on Friday
Astronauts have successfully installed an extension to the International Space Station in a series of spacewalks.
The so-called Tranquility Node includes a number of docking locations and will provide a breathtaking, 360-degree view of Earth through its "cupola".
The node was initially installed on Friday, with electrical connections and commissioning occurring in a series of spacewalks over the weekend.
A final spacewalk on Tuesday will complete the node's commissioning.
The US space agency Nasa has extended the mission of space shuttle Endeavour by a day to allow all the crew's tasks to be completed.
Installation of Tranquility and the cupola, both supplied by the European Space Agency, marks the end of major construction of the ISS, an international effort that first began in 1998.
The 14-tonne node will house core life-support systems, exercise equipment, robotic workstations and - in the form of its cupola - the best view of Earth and approaching spacecraft that the ISS has ever enjoyed.
A spacewalk of nearly six hours undertaken on Saturday saw Tranquility connected to the ISS's cooling system.
NODE 3 - 'TRANQUILITY'
Key unit connects and helps manage other ISS modules
Multiple docking ports for visiting vehicles or future modules
7m by 4.6m; a mass of 14 tonnes, but will be fitted out in orbit
Sophisticated life support systems will include air cleaning unit
Cupola to be fixed to an Earth-facing port once in orbit
Panoramic views provide ideal control room for robotic arm
Named after Sea of Tranquility, the Apollo 11 landing site
A small mishap occurred when ammonia from the system shot out on to mission specialist Nicholas Patrick's spacesuit.
The liquid ammonia had already solidified by the time it hit the suit and bounced off, but the spacewalk was cut short to carry out safety procedures.
With cooling in place, Tranquility's electrical systems could be powered up.
In a spacewalk late on Sunday, the crew moved the cupola into place on the Earth-facing side of the node.
Space station commander Jeffrey Williams found that several of the bolts holding the cupola in place were jammed.
With instructions from ground control, the crew increased the force applied and were able to free the bolts - only to find an electrical connector appearing to hang loosely from the dome.
Commander Williams assured crew that the wiring would not interfere with the cupola's Earth-side installation, and the cupola was put into place without further incident.
Tuesday's spacewalk will see the crew install a robotic workstation and a back-up cooling system on the node.
On Wednesday or Thursday, the cupola's shutters will be drawn back, giving a view through the largest window ever to be sent into space.
"The cupola, I think, is really one of the most spectacular viewing platforms that we will have had in space... so we're eagerly awaiting the release of the shutters and the first views," said flight director Kwatsi Alibaruho.
The shuttle is now due to land at Kennedy Space Center on 21 February.
There are four more shuttle missions to the ISS planned in the coming seven months before the shuttle fleet is retired.