Mir’s main control and living area were housed in the 13-metre cylinder of its core module, with a docking node to allow for the station’s progressive expansion with extension modules. In addition to the main command systems, this 100-m3 living space contained everything the crew needed to conduct science experiments, prepare meals, sleep and exercise.

Between 1986 and 1996, the following extension modules were launched and then assembled in orbit to complete the 30-metre-long complex:

• Connected to one end of the core module in 1987, Kvant 1 contained a space astrophysics laboratory as well as equipment for performing biotechnology experiments.
  
• Divided into 3 compartments, Kvant 2 was added in 1989 to provide additional life support systems, an airlock for extravehicular activities (EVAs), plus a biology research laboratory.
  
• In 1990, the Kristall module came equipped with 2 solar panels plus scientific equipment for processing materials and biological products in the space environment.
  
• Spektr, added in 1995, was dedicated mainly to Earth observation, notably the study of its natural resources, atmosphere and gamma and X-rays. This module generated the most electricity, thanks to its large solar panels.
  
• The last module to be berthed, in 1996, Priroda extended the station’s Earth observation capabilities, specializing in the study of ecological and environmental problems.