Lichtenstein's work defined the premise of pop art through parody. Inspired by the comic strip, Lichtenstein produced precise compositions that documented while they parodied, often in a tongue-in-cheek manner.

His work was influenced by popular advertising and the comic book style. He described pop art as "not 'American' painting but actually industrial painting". His paintings were exhibited at the Leo Castelli Gallery in New York City.

Whaam! and Drowning Girl are generally regarded as Lichtenstein's most famous works, with Oh, Jeff...I Love You, Too...But... arguably third. Drowning Girl, Whaam! and Look Mickey are regarded as his most influential works. His most expensive piece is Masterpiece, which was sold for $165 million in January 2017.

By blending high and low art, Roy Lichtenstein tested the contradictions at the heart of our ideas about art. He was labelled a heretic, but half a century later, we get the joke

At the same moment that Lichtenstein was discovering that he could use popular culture to ask searching questions about concept, form and technique, Andy Warhol was, quite independently, also using cartoon in his experimental work: neither artist knew it yet, but Pop Art was about to spring fully formed from America's forehead.

The nation did not initially enjoy looking in the mirror that Lichtenstein and Warhol were thrusting toward it: in 1964, Life magazine asked of Lichtenstein, "Is he the worst artist in America?

In the beginning, cartoons and comic strips provided his source material, although he soon moved away from them.

But he never abandoned his signature method, the Ben-Day dot (named after inventor Benjamin Day's 1879 technique for reproducing printed images by using dots to recreate gradations of shading), ensuring that his work would remain as recognisable as it was quotable.

Lichtenstein's paintings are far more technically demanding than it seems at first glance.

His work was described by the critic Hal Foster as the "handmade readymade": not industrially mechanised, but blending careful techniques of handwork (drawing, tracing, painting, emphasising brushstroke, line, and Ben-Day dot) with the reproduction and screening of found images.

It is not art trouvé but art retrouvé: refashioned, recovered, reframed. And in the process, our simplistic distinctions between making and manufacturing begin to dissolve.

Like Marcel Duchamp before him, Lichtenstein was criticised for not producing original art but plagiarising the originals.

Unlike Dadists like Duchamp, Lichtenstein couldn't even offer the avant-garde defence of aggressive "obscenity": his work is resolutely unconfrontational, tonally serene, even when the subject matter (such as Drowning Girl or WHAAM!) is pain or violence.

This led to persistent accusations of detachment, distance, a frigidity that some say makes his work hard to love. Conversely, others charge that Lichtenstein's art is too lovable: too accessible, commercial, art "lite" for the merely acquisitive.