Complex sentence: The first major work by Saarinen, started together with his father, was the General Motors Technical Center in Warren, Michigan, designed in the rationalist Miesian style: in steel and glass, but with the added accent of panels in two shades of blue.
Split into simpler sentences: The first major work by Saarinen, in collaboration with his father, was the General Motors Technical Center in Warren, Michigan. It follows the rationalist design Miesian style: incorporating steel and glass, but with the added accent of panels in two shades of blue.