There were smiles all around as the Endeavour crew completed its docking procedures with the space station, crawled through a hatch and came aboard.
Shuttle commander Mark Kelly - the husband of wounded U.S. Rep. Gabrielle Giffords- was the first to float into the space station. He was greeted with handshakes and hugs.
Kelly and his five crewmates will spend nearly two weeks at the space station.
On Thursday, the two orbiting crews will attach the $2 billion Alpha Magnetic Spectrometer to the space station. The instrument will seek out invisible dark matter as well as antimatter; whether any of this is found or not, the results will help explain what the universe is made of and how it formed.
It is the 12th and final visit by Endeavour to the space station. After this mission, Endeavour will be de-commissioned and sent to the California Science Center in Los Angeles.
Atlantis will carry out NASA's final shuttle trip in July.
The Associated Press contributed to this report.