Final answer:
The Barbizon painters and Impressionists like Monet and Renoir practiced plein air painting, revolutionized by the invention of paint tubes, which led to the development of Impressionism.
Step-by-step explanation:
The Barbizon group of painters and the subsequent Impressionists, including Claude Monet, Pierre-Auguste Renoir, Alfred Sisley, and Frédéric Bazille, embraced the technique of plein air painting. This approach, which involves painting outdoors and directly from nature, was a radical departure from the traditional method of painting in a studio. The invention of paint tubes by John Goffe Rand in 1841 was a crucial development that allowed artists to easily transport and use oil paints outside, thereby facilitating the plein air method and leading to the revolutionary art movement known as Impressionism.