Aarnio studied at the Institute of Industrial Arts in Helsinki, and started his own office in 1962. The following year he introduced his Ball Chair, a hollow sphere on a stand, open on one side to allow a person to sit within. The similar Bubble Chair was clear and suspended from above. Other innovative designs included his floating Pastil Chair (similar to a solid inner tube), and Tomato Chair (more stable with a seat between three spheres). His Screw Table, as the name suggests, had the appearance of a flat head screw driven into the ground.

Aarnio's designs were an important aspect of 1960s popular culture and could often be seen as part of sets in period science-fiction films. Because his designs used very simple geometric forms, they were ideal for such productions.