Contemporary architecture retains modernism's devotion to connecting the indoors and outdoors, and the desire to achieve a feeling of spaciousness - yet it isn't averse to showing signs of regional character or even whimsy. Today's architects are especially concerned with energy efficiency and sustainable materials, which has led to some truly innovative design. Key elements include natural, sustainable components, recycled and nontoxic materials and natural light. Many contemporary homes seek a communion with nature, not just in forms that echo the natural environment, but in the type of materials used. Green, or eco-friendly, building is an enormous trend, using materials and methods that create a sense of harmony and relaxation. Contemporary design can be similar to modernism; recalling the early- and mid-20th-century architecture embodying the ideals of the machine age, such as an absence of ornament, structures of steel or concrete, large expanses of glass, a whitewash (usually stucco over brick) or another minimal exterior expression, and open floor plans.