Biophilia was first defined by biologist and Harvard professor Edward O. Wilson in 1984 as the "innately emotional affiliation of human beings to other living organisms."  This emotional affiliation results in increased happiness, ability to learn, and reduced stress levels when individuals are frequently in contact with elements of nature such as sunlight, outdoor air, plants, and water. 

Biophilic design incorporates the idea of biophilia, and human affiliation to nature, into building design.  Common biophilic designs include features that allow for the entry of diffuse sunlight, opportunities for contact with nature, use of passive natural ventilation, the use of local natural materials, and views of the outdoors from the interior of the building.

Biophilic elements can be integrated in the design of the building itself, the landscaping of the site, and the design of the interior.  This is often accomplished by:

• Increasing the amount of natural daylight entering a building through windows and skylights;
• Adding indoor vegetation by including small gardens, potted plants, or planted walls;
• Planning for outdoor greenspace, including gardens, grassy areas, and trees;
• Maximizing quality window views, particularly views of nature;
• Using nature in murals and pictures; and
• Using natural materials in the interior and exterior (1).

Sources:
¹ Heerwagen, J., Kellert, S.R. and Mador, M., 2008. Biophilic Design: The Theory, Science and Practice of Bringing Buildings to Life. New York: John Wiley & Sons, Inc.