The second in the series of International Microgravity Laboratory payloads (IML-2) was launched on the Space Shuttle Columbia's STS-65 mission on 8 July 1994. After remaining in orbit around the Earth for 15 days, the Shuttle landed on 23 July. The seven-member crew included a Japanese astronaut, who was the first Japanese woman in space.

Besides NASA, the European Space Agency (ESA) and the space agencies of Japan (NASDA), Canada (CSA), Germany (DLR), and France (CNES) sponsored experiments on the mission. Investigators from a total of 13 countries participated in research into the behavior of materials and life in microgravity.

The IML-2 payload consisted of more than 80 experiments in microgravity and life sciences, including five life science experiments developed by American researchers. Of these, Ames Research Center sponsored two experiments using newts and jellyfish. Kennedy Space Center (KSC) sponsored the PEMBSIS experiment, designed to study plant embryogenesis in microgravity.

The International Microgravity Laboratory (IML-2) was the second in a series of Spacelab (SL) flights designed to conduct research in a microgravity environment. The IML concept enabled a scientist to apply results from one mission to the next and to broaden the scope and variety of investigations between missions. Data from the IML missions contributed to the research base for the space station.

As the name implies, IML-2 was an international mission. Scientists from the European Space Agency (ESA), Canada, France, Germany and Japan collaborated with NASA on the IML-2 mission to provide the worldwide science community with a variety of complementary facilities and experiments. These facilities and experiments were mounted in twenty 19" racks in the IML 2 Module.

Research on IML-2 was dedicated to microgravity and life sciences. Microgravity science covers a broad range of activities from understanding the fundamental physics involved in material behavior to using those effects to generate materials that cannot otherwise be made in the gravitational environment of the Earth. In life sciences research, a reduction of gravitation's effect allows certain characteristics of cells and organisms to be studied in isolation. These reduced gravitational effects also pose poorly understood occupational health problems for space crews ranging from space adaptation syndrome to long-term hormonal changes. On IML-2, the microgravity science and life sciences experiments were complementary in their use of SL resources. Microgravity science tends to draw heavily on spacecraft power while life sciences places the greatest demand on crew time.

Life Sciences Experiments and facilities on IML-2 included: Aquatic Animal Experiment Unit (AAEU) in Rack 3, Biorack (BR) in Rack 5, Biostack (BSK) in Rack 9, Extended Duration Orbiter Medical Program (EDOMP) and Spinal Changes in Microgravity (SCM) in the Center Isle, Lower Body Negative Pressure Device (LBNPD), Microbial Air Sampler (MAS), Performance Assessment Workstation (PAWS) in the middeck, Slow Rotating Centrifuge Microscope (NIZEMI) in Rack 7, Real Time Radiation Monitoring Device (RRMD) and the Thermoelectric Incubator (TEI) both in Rack 3.

Microgravity experiments and facilities on IML-2 included: Applied Research on Separation Methods (RAMSES) in Rack 6, Bubble, Drop and Particle Unit (BDPU) in Rack 8, Critical Point Facility (CPF) in Rack 9, Electromagnetic Containerless Processing Facility (TEMPUS) in Rack 10, Free Flow Electrophoresis Unit (FFEU) in Rack 3, Large Isothermal Furnace (LIF) in Rack 7, Quasi Steady Acceleration Measurement (QSAM) in Rack 3, Space Acceleration Measurement System (SAMS) in the Center Isle, and Vibration Isolation Box Experiment System (VIBES) in Rack 3.

Other payloads on this mission were: Advanced Protein Crystallization Facility (APCF), Commercial Protein Crystal Growth (CPCG), Air Force Maui Optical Site (AMOS) Calibration Test, Orbital Acceleration Research Experiment (OARE), Military Application of Ship Tracks (MAST), Shuttle Amateur Radio Experiment-II (SAREX-II). Columbia flew with an Extended Duration Orbiter (ED0) pallet and no RMS Arm was installed. This was also the 1st flight of the payload bay door torque box modification on Columbia and the 1st flight of new OI-6 main engine software.