First one-piece plastic bag

The now ubiquitous single-piece polythene carrier bag, with handles worked into the design of the bag - commonly referred to as a "T-shirt bag" - was invented by the Swedish engineer Sten Gustaf Thulin (1914-2006) in 1959. The packaging company at which Thulin was employed at the time, Celloplast, filed a patent for the "bag with handle of weldable plastic material" on 10 July 1962 and it was granted on 27 April 1965. Its light weight, low cost, durability and ease of mass production meant that the plastic bag quickly began to replace cloth and paper bags in Europe and beyond.

Despite now being one of the largest contributors to landfill and ocean pollution, ironically plastic bags were devised as a way to help the environment, by drastically reducing the number of trees being felled to produce paper bags.

Polyethylene (aka polythene) was first discovered by accident during experiments with hydrocarbons by German chemist Hans von Pechmann in 1898. It was then rediscovered, also by accident, by Eric Fawcett and Reginald Gibson at British firm Imperial Chemical Industries in 1933, after which a method was developed to synthesize the substance on an industrial scale. This radically stepped up in the early 1950s when catalysts were found that helped make large-scale production of polyethylene far more economical.