A Welcoming Atmosphere: How to Create (or Boost) It In Your Home

Atmosphere is the je ne sais quoi ingredient to interiors. You can't really put your finger on it and it's not really something you can buy in a box to add to your home. But it's the thing that differentiates a great home from just a good one, and it's the thing that makes guests want to stay and linger in your home as long as possible. How do you get it (or make your existing atmosphere even better)?