In 1948, Joseph Probst participated in the Salon de la Nouvelle Équipe, an avant-garde exhibition organized by Lucien Wercollier with a group of befriended Luxembourg painters. The purpose was the same as the one that led to the Secession in 1927, namely to present a selection of high-quality works by a limited number of artists, a coherent whole rather than showing all the styles of all the members of an association such as the Cercle Artistique de Luxembourg (C.A.L.). In 1950, the Nouvelle Équipe organized a second Salon. Later, in 1954, it was especially the Salon des Iconomaques that introduced abstract art to the public.

Probst was one of the leading figures of this Luxembourg School of Non-Figurative Painting, a movement that marked the history of art in the Grand Duchy. Around 1958, after having studied at the Academies of Brussels and Vienna, he moved away from geometric leanings towards lyrical abstraction.

Around 1963, Probst began mixing oil with sand and scraps of paint, inaugurating a very productive period that resulted in works like this 1963 painting entitled The Red Nucleus. A wonderful example of this period, it presents more or less clearly defined shapes that stand out against a background that is no longer unified. The shapes are linked to each other and overlap. The lyric character of the painting results from this gentle combination of colours and tonalities.