He enrols in the evening classes of the Brussels Académie des Beaux-Arts and in the day-time classes of decorative arts, then does his military service in the Fonck barracks in Liège.

His first attempts at comic strips are published in denominational papers: LA SEMAINE DU CROISE (“Jojo”, 1935-1939, character and graphics still influenced by Hergé) and PETITS BELGES (“Blondin et Cirage”, three episodes from 1939 to 1942).

He produces many covers and woodcuts for CAHIERS WALLONS from1937 to 1943, helped by his father Eugène Gillain, dialect poet and tax collector.

His creative mind enters the service of Éditions Dupuis. After illustrating a serial in LE MOUSTIQUE, he successively realises for SPIROU: “Freddy Fred et le mystère de la clef hindoue” (1939); “Trinet et Trinette dans l’Himalaya” (1939-1941); a first interim of the adventures of “Spirou et Spip” in late 1940, when its creator Robert Velter, better known as Rob-Vel, recovers from a war injury; “Don Bosco, ami des jeunes” (his first drawn biography, in 1941-1942), followed by his monumental “Christophe Colomb” (1942-1945).

In 1941, based on a script by Jean Doisy, he embarks on realistic fiction with “Jean Valhardi, détective”, which will have a profound impact on the young readers of the time. Truly saving the editors during the occupation, he finishes the continuations of several American series that had not been published on the continent yet (“Superman”, “Cavalier Rouge”) and takes up the adventures of “Spirou” again in the summer of 1943. Taking Jean Doisy’s counsel, he creates a crazy partner for Spirou, Fantasio, in order to give his exemplary star a counterpart. From that moment on he handles the realistic and humoristic styles of comic strips with enthusiasm and talent.

Already responsible for the artistic training of young Willy Maltaite, the future Will, he becomes the adviser of the Dupuis brothers immediately after the war, and the catalyst of a team of new talented illustrators: André Franquin, Maurice De Bevere, dit Morris, Eddy Paape and Victor Hubinon.

The artists of varying origin, later on joined by Pierre Culliford, or Peyo, and Jean Roba, constitute the “Marcinelle School” of the Belgian comic book, in view of the editors’ offices and as opposed to the “Brussels School” formed by Hergé and his disciples of the paper TINTIN. In contrast to the clear lines and realism of the latter, the Marcinelle School is characterised by its strongly personalised graphics with flexible strokes, and a predominance of humour and fantasy.

A close friendship grows between Gillain (who mostly signs as Jijé from now on, derived from his initials), Morris, Franquin and Will, in the years 1946-1952. “The gang of four” initially resides in the house of Jijé in Waterloo. The master divides his stars: “Spirou et Fantasio” are allocated to Franquin in 1946; Eddy Paape continues “Jean Valhardi” until 1955, and Victor Hubinon even illustrates an episode of “Blondin et Cirage” in 1947.

The artist embarks upon a colossal biography of Jesus Christ using the wash technique (“Emmanuel”, 1947) and works out a second version of his “Don Bosco” (1949) after a study trip to Italy. Together with Franquin and Morris, his family stays in Mexico for three years and then in the United States. This is where he does most of the work on his biography of Baden-Powell.

Back home he further develops his humoristic style with new episodes of “Blondin et Cirage” (five books from 1951 to 1955), illustrates a serial about the “Comte de Monte-Cristo” in LE MOUSTIQUE (1951-1952) and makes wash drawings for LES BONNES SOIRÉES and works on a story of Flora Sabeiran (“El Senserenico”, 1952), before developing the first major European realistic western comic-strip: “Jerry Spring” (twenty-one books from 1954 to 1977).

His huge work, full of wonderful graphic richness and strong humanist feeling, has a great impact on many a young artist: Jean Giraud or Gir, Derib, Hermann, etc. Though an all-round author, Jijé occasionally appeals to scriptwriters such as Maurice Rosy, René Goscinny, Jean Acquaviva, Daniel Dubois, Jacques Lob and most of all his son Philippe, or Philip.

When he buys an old orangery in a suburb of Paris, Champrosay Draveil, in 1955, this lively nomad finally settles down. For twelve years he produces work for SPIROU: “Jean Valhardi” is brought back to life thanks to his efforts (nine stories from 1956 to 1965), the last three realised together with his friend Guy Mouminoux); the mishaps of “Jerry Spring” are continued; two African adventures of “Doctor Gladstone” are written (with help from illustrator Herbert and scriptwriter Charles Jadoul); the biography of Charles de Foucauld (1959) and “Blanc Casque” in LE MOUSTIQUE (1954) and “Bernadette” in LINE (1958).

He takes up two series edited by Jean-Michel Charlier: “Tanguy et Laverdure” – 1967 (thirteen books from 1967 to 1979) and “Barbe-Rouge” -1979 (three episodes). His work also appears in BONUX BOY, TOTAL JOURNAL, LE JOURNAL DE JOHNNY, TELE 7 JOURS, LA VOIX DU NORD (“Le Commissaire Major”, 1971-1973), etc. As of 1974, however, he takes up the cycle of “Jerry Spring” again in SPIROU and creates three last adventures before his death on the 19th of June, 1980, in Versailles.

Apart from this impressive work (more than 70 creations published in 40 years) the “father of the Belgian comic strip” is devoted, in his spare time, to painting, sculpting and devising practical yet surprising inventions, which were never really used. “Tout Jijé”, the complete chronological collection of his work at Dupuis, is nearly finished.