Plein Air is a French term meaning "in the open air." It refers to the practice of painting outdoors, capturing the natural light and atmosphere of a scene. Artists often use this technique to depict landscapes, cityscapes, and other outdoor subjects, allowing them to observe and represent the changing conditions of light and weather. This approach became popular in the 19th century, particularly among the Impressionists, who sought to break away from traditional studio painting. Notable artists like Claude Monet and Pierre-Auguste Renoir embraced plein air painting, leading to a new appreciation for spontaneity and the beauty of nature in art.