The ISS modules, one by one

Published October 12, 2026 · Updated October 12, 2026

A station built piece by piece

The ISS wasn't launched in one go. It was assembled in orbit one piece at a time, like a giant Erector set, over more than twenty years. The first module went up in November 1998 and the last ones in 2021. Today the station has 16 main pressurized modules, plus an inflatable module and a commercial airlock, all attached to a huge 109 m (358 ft) truss that holds the solar arrays and radiators.

Inside, it's split into two halves that are run almost independently: the Russian segment, controlled from Moscow, and the US segment, controlled from Houston, which also includes the European and Japanese labs. The two halves meet at a single point, the joint between Zarya and Unity.

The Russian segment

This is the oldest part of the station, and it carries the main engines. Its modules are descendants of those on the Soviet Salyut and Mir stations.

• Zarya (1998). The first module, launched on November 20, 1998. It was built in Russia with NASA funding and originally supplied power and propulsion. Today it serves mainly as a storage area and fuel depot.
• Zvezda (2000). The service module, docked in July 2000. It has crew quarters, a galley, life support systems and the engines that raise the orbit when needed. It was the station's first real “home.”
• Poisk (2009). A small module on top of Zvezda that works as a docking port for Soyuz and Progress spacecraft and as the airlock for Russian spacewalks.
• Rassvet (2010). It arrived aboard the space shuttle Atlantis. It's a docking port under Zarya and doubles as a small storage room.
• Nauka (2021). Russia's multipurpose laboratory, launched in July 2021 after more than a decade of delays. It carries the European Robotic Arm (ERA). To make room for it, Pirs, the old docking module from 2001, was removed.
• Prichal (2021). A spherical node with six hatches, attached to Nauka in November 2021, that gives the Russian segment more docking ports.

The US segment and its partners

This is where most of the labs are. Several “American” modules were actually built in Italy: Harmony, Tranquility, the Cupola and Leonardo came out of the same factories in Turin as Europe's Columbus lab.

• Unity (1998). The first node, attached to Zarya in December 1998. It links the two halves of the station.
• Destiny (2001). NASA's laboratory, the hub of US experiments and of the segment's control systems.
• Quest (2001). The airlock astronauts use for spacewalks in US suits.
• Harmony (2007). The node that connects Destiny to the European and Japanese labs. Crew Dragon and cargo Dragon spacecraft dock at its forward and top ports.
• Columbus (2008). The European Space Agency's laboratory, with room inside for experiments and platforms on the outside.
• Kibo (2008–2009). Japan's laboratory, delivered in three trips: a pressurized storage section, the main module and an external platform exposed to space. Its main module, 11 m (36 ft) long, is the largest on the entire station. It has its own robotic arm.
• Tranquility (2010). A node that holds much of the segment's life support: water recycling, oxygen generation, the toilet and the exercise machines.
• Cupola (2010). The observation deck: seven windows, the central one 80 cm (31 in) across. The Canadarm2 robotic arm is operated from here, and it's where the best photos of Earth are taken.
• Leonardo (2011). A former space shuttle cargo module that stayed behind as a permanent storage room.
• BEAM (2016). An experimental inflatable module. It was launched folded up and inflated in orbit. It was supposed to be a two-year test and ended up as a storage closet.
• Bishop (2020). The first commercial airlock, used to put small satellites and experiments outside the station.

When each piece arrived

The parts that aren't modules: truss, solar arrays and arms

Besides the modules where the crew lives, the ISS has a large external frame: the integrated truss, 109 m (358 ft) from end to end, nearly the length of a football field. It carries the eight large US solar arrays, boosted since 2021 by newer roll-out arrays, along with the radiators that get rid of excess heat and the platforms where spare parts are stored.

Also working on the outside is Canadarm2, Canada's 17 m (56 ft) robotic arm, which grabs cargo ships and moves equipment around, together with Dextre, its precision “hand.” The Russian segment uses the European Robotic Arm (ERA), installed on Nauka.

If you're curious how all of this keeps running (the power, the air, the water), we explain it in how the ISS works.

Frequently asked questions

How many modules does the ISS have?

Sixteen main pressurized modules: six in the Russian segment and ten in the US segment, counting Kibo's two pressurized modules. On top of those come the BEAM inflatable module and the Bishop commercial airlock.

What was the first module of the ISS?

Zarya, launched from Baikonur on November 20, 1998. Two weeks later, the space shuttle Endeavour carried Unity up and attached it to Zarya. That was the birth of the station.

Which module is the largest?

The main pressurized module of Kibo, Japan's laboratory. It's about 11 m (36 ft) long and just over 4 m (13 ft) in diameter.

Has any module ever been removed?

Yes. Pirs, the Russian docking module and airlock from 2001, was undocked in July 2021 and burned up on reentry into the atmosphere, freeing its spot for the Nauka laboratory.

Where can I see what each module looks like inside?

On our ISS page, which has a 3D model based on NASA's and a first-person tour through the inside of the modules.