Interior design with nature in mind™

Americans, on average, spend approximately 90 percent of their time indoors.1   But evolutionarily speaking, human beings developed while spending 90 percent of their time outdoors. To this day, we are genetically primed to thrive in nature by recognizing cues that signal to our brain (specifically our limbic and endocrine systems2) that we are either: safe, or, in danger. The neurobiological research on this phenomenon is substantial.3

Knowing this,  how are we taking advantage of our innate response to nature, while we're indoors? What are we doing to leverage the effects that nature and natural analogues have on our stress/relax hormones when we're inside?