Since the US’ Unity module connected to Russia’s Zarya control module in 1998, the ISS has been incrementally assembled in space and contains 43 components as of 2025. These include solar arrays for power, four labs, six sleeping quarters, two bathrooms, and a gym where mandatory exercise helps astronauts maintain muscle mass in microgravity. Observational instruments have collected geological, meteorological, climate, and cosmic particle data.
Over 280 individuals from 26 countries have visited the ISS and conducted over 4,000 experiments, ranging from growing protein crystals for pharmaceuticals to testing the effectiveness of microbes at mining space minerals. The ISS is expected to be retired in 2030.