Frank Stella's art in the 1960s represents a transformative period that firmly established his reputation as a pioneering figure in the minimalist and post-painterly abstraction movements. Stella, who had moved to New York in 1958, first made waves in the art world with his "black paintings," a series characterized by their austere simplicity and use of symmetrical stripes that mirrored the shape of the canvas against black backgrounds. These paintings, such as "The Marriage of Reason and Squalor, II" (1959), were instrumental in Stella's early recognition, including inclusion in the landmark "Sixteen Americans" exhibition at New York's Museum of Modern Art (MoMA) in 1959​ (Encyclopedia Britannica)​. Throughout the 1960s, Stella's work evolved from the stark monochromatism of his black paintings to embrace a broader palette and more complex forms. He introduced the Aluminum Paintings (1960) and the Copper Paintings (1960-61), characterized by geometrically shaped canvases that broke away from traditional rectangular formats. These works continued to explore the stripe motif but in a context that began to flirt with more dynamic and circular motifs, heralding the onset of what would become his Irregular Polygon (1965-67) and Protractor (1967-71) series. The shift was part of a broader reaction against the emotional intensity and gestural brushwork of Abstract Expressionism, aiming instead for a clarity and precision in form and color​ (The Art Story)​. By the mid-1960s, Stella had become a leading figure in Post-Painterly Abstraction, a movement seeking to distill painting to its essentials and reduce the dominance of Abstract Expressionism. His exploration of shapes expanded to include zigzags, stripes, and arcs, often executed in vibrant hues. This period marked a significant development in Stella's conceptualization of painting, as he began experimenting with assemblages of forms that extended into space from the painting's surface. He utilized a variety of materials, including steel and plastic, to achieve his vision of liberating painting from the traditional constraints of the wall​ (Smithsonian American Art Museum)​. Stella's printmaking also began in earnest during the 1960s, closely related to his paintings but growing in complexity over the years. His approach to printmaking reflected his broader artistic evolution, initially using printing techniques as a means of painting before shifting towards exploiting the unique capabilities of the medium to explore new artistic territories​ (Smithsonian American Art Museum)​. The 1960s set the stage for Stella's future explorations in three-dimensionality and multimedia art, establishing foundational elements that would recur throughout his career. His work from this era not only challenged prevailing notions of painting but also contributed significantly to the trajectory of modern art, influencing a wide range of artists and movements that followed.