Josip Seissel was born on January 10, 1904 in Krapina, Croatia. Seissel was an architect, urban planner, zenitist, surrealist, and a distant forerunner of the Croatian avant-garde, anticipating the avant-garde in theory and practice before the term had even been established at home and abroad. He earned his degree in architecture at the Technical Faculty in Zagreb in 1929. He was employed at the Department for the Regulation of Zagreb, and later he was appointed director of the School of Applied Arts. After 1945 he worked at the Ministry of Construction, and from 1965 as a professor at the Faculty of Architecture in Zagreb. In 1962 Seissel became a full member of the Croatian Academy of Science and Arts. With his co-workers Seissel designed the urban plans of certain parts of Zagreb (University and Pioneer Town), studies for  the regions of Makarska, Baško Polje, Šibenik, Mljet and Niksic (Montenegro), and independently, plans for the cemetery  Miroševac, Maksimir Park, a memorial area in Zagreb, Plitvice Lakes and many others.

In parallel with his architectural career, throughout life Seissel was interested in visual art and left behind a great drawing and painting ouevre. He participated in the avant-garde movements related to the Group Travelers and Zenit magazine, under the pseudonym Jo Klek. He is considered to be the founder of Croatian Constructivism and pioneer of Surrealism. Seissel is the author of the painting "Pafama" (short for Papierfarbenmalerei) dated 1922, considered to be the first abstract composition of Croatian modern art. It is characterized by clearly constructivist formal features,   which at that time constituted a synonym for European avant-garde art. The importance of "Pafama" is not only in marking the appearance of the avant-garde in Croatia, but also for its long lasting impact on Croatian art production of the XX century, especially the 50's and 60's during which neo-constructivist tendencies dominated.

Josip Seissel was a successful illustrator, responsible for the constructivist design of Marijan Mikac's books and Zenit magazines. The bulk of his artistic oeuvre consists of surrealist works created during a time span of over half a century, and now part of the Museum of Contemporary Art Collection in Zagreb. His art included drawing, watercolors, pastels, tempera and collage.  The most famous cycle consists of 19 verbo-visual works in watercolor, ink and tempera called 3C  i tričarije (a play on words difficult to translate: Chaff and Tow). His humorous word puzzles were his own invention and without any exemplar within the Surrealist movement.

Seissel is considered the forerunner of Happenings, ten years in advance of its global inauguration in 1958 at Reuben Gallery. In mid-July of 1949 during his summer holidays in Brela, inventive Seissel had organized the first so far known and photographically documented happening in Croatia, with the help of the architect Tušek and a group of mutual friends. This historical happening was a forerunner and contained all of theelemental premises formulated by Allan Kaprow nine years later: "The boundary between the happening and everyday life should be set up so flexibly that one can not precisely determine it... Happening should be enacted in both an inartistic and practical way, it shouldn't be rehearsed and it should be acted out by non-professionals, and only once.. " Seissel's happening with the Zagreb group was performed with a stone on their heads and in their hands, and it was immediately understood as an artistic act.

Josip Seissel cut with the sharpness of a surgical scalpel deeply under the skin of conformity, originating either from  tradition or current trends. As an accomplished architect, urban planner and teacher at the Zagreb Faculty of Architecture, he educated numerous generations of urban planners. In his profession Seissel was known as an ardent supporter of "rationalist" principles of modern architecture, but from its beginnings his artistic practice was firmly on the other side  of "rationalism", unreservedly committed to the "dark object" of his subconscious. His humor was amazing, unpredictable and genuine, outside of the molds and the premises of a time "castrated with programs and manifestos."

Josip Seissel died on February 19, 1987 in Zagreb.