How did Piet Mondrian’s first neoplastic paintings differ from his later grid paintings?

Piet Mondrian’s earliest Neoplasticism paintings differed significantly from his later grid-based works in their composition and use of structural elements.

In his initial Neoplastic paintings, Mondrian composed works using rectangles of soft primary colors set against a white background without the use of lines. These early compositions relied entirely on color and were designed to appear as though they expanded beyond the borders of the canvas.1

By 1918, Mondrian introduced the black vertical and horizontal lines that would become the hallmark of his grid paintings. These lines served to link color planes to one another and to the background, creating a structured system of rectangles. As his style matured, these grids became more defined, organizing the canvas into a formal, nonrepresentational balance of lines and primary colors. In his final phase after moving to New York City in 1940, Mondrian further evolved this style by replacing austere black lines with rhythmic, colored bands and small, vibrant rectangles of color.123