Yes, forest bathing may be good for your health, but what exactly is forest bathing? As the Wall Street Journal explains, it’s a walk in the woods– a long walk in the woods with a focus on breathing in the chemicals that trees breathe out. Justin Bieber is on board. So is Gwyneth Paltrow. And the government of Japan is so deep in the woods that it has spent millions promoting “shinrinyoku,” as the activity is known in Japan. The Journal cites a study, published in the Journal of Biological Regulators and Homeostatic Agents that analyzed findings of forest bathing from 13 female nurses between ages 25 and 43 and showed that exposure to phytoncides, chemicals emitted by some plants to protect themselves from insects and germs, increased the activity of antimicrobial proteins released by killer cells of the immune system. Another study published by Nippon Medical School in Tokyo found that a group of 19 middle-aged men had higher levels of a fat-burning hormone after the walk in the forest. A few years ago, forest bathing made its way across the Pacific and landed securely in California, spawning the Association of Nature and Forest Therapy. The Washington Post reports that for a tuition fee, the organization offers forest therapy guide certification programs in Northern California and Massachusetts.