Octet Truss / tetra-units

Octet Truss is a space frame of space structure for lightweight rigid structure.
It was invented by Alexander Graham Bell around 1900 and Buckminster Fuller in the 1950s. Bell was primarily using them to make rigid frames for aeronautical engineering while Fuller was focused on building architectural structures.
The largest structure to apply octet truss was the Space frame roof of the Festival Plaza, during the Osaka Expo in 1970. The Space frame roof was designed as a temporary structure and was dismantled in 1979.