The $2.4bn Japanese space lab was first conceived two decades ago and has been hit by a series of delays, mostly caused by the 2003 Columbia shuttle disaster which put a hold on launches for two years.
Kibo is the most sophisticated Japanese spacecraft ever built and marks the country's first permanent manned presence in space.
Japanese astronaut Takao Doi, is among the seven-strong crew on Endeavour's mission to deliver the first part of Kibo to the ISS.
"I understand that this is a really big event for Japan because it's just like we'll have a little Japanese land in space," Doi, who is on his second shuttle flight, told reporters before the launch.
He admitted the first part of the laboratory was a tight squeeze, offering about as much space as a "walk-in closet".
For Japan the launch of Kibo gives the country a prized spot alongside the United States, Russia and Europe after committing more than $10bn to the ISS project.
"This flight will be a monumental flight for Japan," Tetsuro Yokoyama, deputy manger of operations for the Kibo project, told reporters in Houston last week.
Largest single module for ISS
Japan's first permanent manned presence in space
To be delivered into orbit by three shuttle flights
Will conduct experiments on effect of microgravity
Includes platform with robotic arm to expose experiments to space
The crew is scheduled to conduct at least five space walks during its 12 days attached to the ISS, as Nasa looks to ramp up construction efforts on the space station before the ageing space shuttle fleet is retired in 2010.
With a mission length of 16 days, Endeavour's flight will be the longest-ever by a shuttle visiting the space station.
The mission will also deliver a Canadian two-armed robot known as Dextre, designed to assist spacewalking astronauts at the orbiting complex
Two other parts of the Japanese laboratory are due to be delivered by later missions, with the completed unit eventually forming by far the largest of four research modules on board the ISS.
Russia and America both have space laboratories attached to the ISS and last month Europe added its Columbus lab to the platform.
"Our Japanese people have been waiting for a very long, long time," Yoshiyuki Hasegawa, space station programme manager with the Japan Aerospace Exploration Agency (Jaxa), told reporters before the launch.
The first part of Kibo, dubbed ELM-PS, will carry an equipment and storage room for the Japanese lab and weighs 4.2 tonnes.
The main section - a massive 11.2-metre-long, bus-sized cylinder weighing almost 16 tonnes - is scheduled for launch in late May.
The final section, an outdoor porch with robotic arms for tending to science experiments, is due to fly next year.
|Astronaut Takao Doi will oversee installation |
of the Japanese lab [Photo: Nasa]
Once operational the lab will carry out research into the effects of micro-gravity.
Officials have said that several of Kibo's experiments, focusing in part on medicine, biology, biotechnology and communications, are crucial steps in preparing further missions to the Moon and eventual manned missions to Mars.
The additions of Columbus and Kibo mark important steps forward for the European and Japanese space programmes, but also for the $100bn ISS itself, finally bringing its multinational status into reality.
Japan is investing heavily in building up its space efforts, developing its own launch capabilities and planning to fly its own unmanned cargo flights to the space station beginning in 2009.
On Saturday Europe's space agency introduced its own automated supply vessel for the ISS known as the Automated Transfer Vehicle (ATV).
The ATV will deliver seven and a half tonnes of food, water, pressurized air, fuel and personal items to the ISS crew.