During the early 19th century, the German (and especially Austrian) interiors style known as Biedermeier became popular as focus shifted to the importance of nature in an urban setting. During this rise in urbanism, decorative arts and interior design focused on developing the Biedermeier "lifestyle" of curated nature scenes. These included a menagerie of greenery, elaborately tiered houseplants with birdcages and fishbowls, and light-filled bay windows with seating. Nature motifs were carved in fruitwood furniture (moving away from metals), as well as nature scenes hand painted on glass and porcelain.
The essence of our modern notion of "outside in" is not much different. While the overall style has developed with time, we still practice a love for houseplants. There are health benefits, but I believe urbanism plays a big role in our love for indoor greenery. And, of course, it's fun to watch plants grow!