I tried to work with small áreas of glass and adjusted my strips of glass to the light and then pushed them into the plasticine planes of the floors. That gave me the curve…I had no expressionist intention. I wanted to show the skeleton, and i thought that the best way would be simply to put a glass skin on.
Mies Van der Rohe ( ARCHITECTURAL REVIEW : Mies Speaks) 1968.

The office building is a house of work, of organisation, of clarity, of economy. Broad, light work-space, unbroken, but articulated according to the organisation of the work. Maximum effect with mínimum means. The materials: concrete, Steel, glass. Reinforced concrete structures are skeletons by nature. No fortress. Columns and girders eliminate bearing walls. This is skin and bone construction.
Mies Van der Rohe (ARCHITECTURAL MONOGRAPHS 11) 1986 (pag 43)