Of all things physical and metaphysical,
Of all things human and all things super-human,
Of all true manifestations of the head,
Of the heart, of the soul,
That the life is recognizable in its expression,
That form ever follows function. This is the law. (Wikipedia)
It was this statement made by Horatio Greenough, that inspired architect Louis Sullivan, and was adopted as his most imperative rule when designing anything, and specifically in his case architecture. Frank Lloyd Wright, Sullivan's assistant, carried this torch, and applied it to all of his designs. It was arguably the mantras of these three individuals that had a major influence on Walter Gropius and the rest of the Bauhaus movement. The Bauhaus' architectural style was very reductive and obviously had a focus on the functionality within the spaces the created. "Ornament becomes an unnecessary relic, or worse, an impediment to optimal engineering design and equipment maintenance." (Wikipedia)
They looked upon added ornamentation as a crime, and concentrated on the grid and negative space. "Modernism in architecture began as a disciplined effort to allow the shape and organization of a building to be determined only by functional requirements, instead of by traditional aesthetic concepts. It assumes that the designer will determine empirically (or decide arbitrarily) what is or is not a functional requirement. The resulting architecture tended to be shockingly simpler, flatter, and lighter than its older neighbors, possibly due to the limited number of functional requirements upon which the designs were based; their functionality and refreshing nakedness looked as honest and inevitable as an airplane." (Wikipedia) This is even more apparent in the graphic design of the Bauhaus movement, which is credited with the creation of the typographic grid which is prominent in 98% of layout design we see today.
The Bauhaus ideology has even been applied to many common products and items we use today such as kitchen ware, furniture(ie: Lamps, Chairs, Bookshelves, etc.). The teapot pictured below was designed by Marianne Brandt back in 1924. It was made out of silver, which contributes to its Industrial aesthetic and incorporates the circle, square, and globe, which strictly follows the basic forms of construction. I think it is the small common objects like this teapot that are the epidemy of the credos of Bauhaus design. Function ever follows form.