Unity, also known as Node 1, is the first U.S.-built component of the International Space Station (ISS). This cylindrical module, constructed of steel by Boeing for NASA, serves as the critical link between the orbiting laboratory's Russian Orbital Segment and US Orbital Segment.
Unity was launched on December 4, 1998, aboard the Space Shuttle Endeavour on STS-88. Two days later it was berthed to the previously launched Zarya module, marking the first connection between ISS components. Its six Common Berthing Mechanism (CBM) locations (forward, aft, port, starboard, zenith, and nadir) facilitate connections to other modules. At launch, two CBM locations were fitted with Pressurized Mating Adapters (PMA), one of which enabled the mating with Zarya.