L'Arbre rouge

Most people know Mondrian for grids of black lines and blocks of primary colour, so this comes as a surprise: a single apple tree, painted around 1908 to 1910, its bare branches writhing out red against a deep blue evening. The paint is thick and the colour has nothing to do with what a real tree looks like, and you can see how hard Van Gogh had hit him. This is the first of a long series in which Mondrian returned to the same tree again and again, each time paring it back further, until in later versions the branches have become almost a lattice of horizontals and verticals. The grids people picture when they hear his name grew, step by step, out of watching a tree like this one.