"Matisse: Pairs and Series" explores for the first time how one of the greatest painters of the 20th century would repeat the same composition again and again, varying colour and technique, before being satisfied with the result.

For a man best known as leader of the Fauvist movement, and for seemingly spontaneous bursts of colour such as his 1906 "Joy of Life", the show reveals an insecure and restrained side that would remain unchanged throughout a six-decade career.

"We wanted to challenge the received wisdom that he was a happy painter, an easy painter, a sort of virtuoso of simplicity and joy," said exhibition curator Cecile Debray.

"Matisse was obsessive, worried, racked with doubt from the beginning to the end, and he showed it in his painting through this constant multiplication and exploration," she said.

The exhibition, expected to be one of the highlights of the spring cultural season in Paris, runs to June 18 at the Pompidou Centre, before moving on to Copenhagen's Statens Museum for Kunst and then the Metropolitan Museum of Art in New York.

It comprises some 60 paintings and 30 drawings, including emblematic works like Matisse's "Blue Nude" cut-paper series from 1952, four collages labelled I to IV, where he began the last work first then tried three different variations, before coming back to finish his first attempt at the end.

"A painting is like a card game: you should know from the beginning what you wish to achieve at the end. Everything should be worked backwards so that you have finished before you have begun," Matisse is quoted as saying in the exhibition.

"WILD BEAST"

Although the idea of the tortured artist is perhaps nothing new, what's particularly surprising in Matisse's case was his willingness to show the laborious process behind his art.

In 1945, as the exhibition shows, Matisse displayed six of his finished works in a gallery in Paris, alongside framed photographs of their previous stages, showing the genesis of the work and the complexity behind the apparent ease.

Debray attributes the rare honesty to the artist's need for validation after the 1905 Autumn Salon in Paris, where the violent colours of works such as his "Open Window" and "Woman with a Hat" earned him and fellow artists the derogatory nickname "fauves" or "wild beasts".

"He was considered a bit of a joker and there was a real scandal. Maybe (fellow artist Marcel) Duchamp would have loved it, but Matisse wasn't like that and he kept trying to explain himself, to be taken seriously," Debray told Reuters.

Despite the early criticism, Matisse went on to achieve fame and fortune during his lifetime and is often regarded as the most important French painter of the 20th century.

Born in 1869 in Picardy in northern France, he studied law before discovering a love of art in 1890, while recovering from a bout of appendicitis, later achieving success with his first exhibition in 1896 with his "Woman Reading"

After coming under the influence of the Neo-Impressionists or Pointillists, he went on to research new techniques, eventually developing the broader brush strokes and passion for pure colour that would characterise his work.

Matisse died in 1954 in Nice on the French Riviera.

(Reporting By Vicky Buffery, editing by Paul Casciato)

• A Permanent Economic Emergency