Ruben Rausing, a Swedish native, graduated from Columbia University in New York City with a master’s degree in engineering. While in America, he observed that self-service grocery stores were stocked with pre-packaged goods and foresaw the trend spreading to Europe. Rausing returned to Sweden and in 1951, after nearly a decade of research and development, his company debuted the Tetra Classic, a tetrahedron-shaped paper carton that was continuously filled with milk. Within a decade, the Tetra Classic would evolve into the Tetra Brik, a rectangular-shaped carton, and by 1974 into the Tetra Brik Aseptic, the same paper carton but with a thin layer of aluminum.
See: “An Abbreviated History of the Ubiquitous Juice Box” by Oren Peleg on the life & thyme website