Impressionism was a radical art movement that began in the late 1800s, centered primarily around Parisian painters. Impressionists rebelled against classical subject matter and embraced modernity, desiring to create works that reflected the world in which they lived. Uniting them was a focus on how light could define a moment in time, with color providing definition instead of black lines. The Impressionists emphasized the practice of plein air painting, or painting outside. Initially derided by critics, Impressionism has since been embraced as one of the most popular and influential art styles in Western history.