The marriage between Google and Nest just got even more official. As Android Police points out, Google has started selling Nest thermostats on its Google Play store starting at $249. And given that it’s Earth Day and that Nest is an eco-friendly, energy-saving thermostat, Google says that it will plant a tree for every Nest unit sold on Tuesday. Nest, which was founded by former Apple exec Tony Fadell, was acquired by Google earlier this year for $3.2 billion. Earlier reports have indicated that Google isn’t interested in Nest just for its smart thermostats but also for its team’s design prowess that won it accolades from several Apple fans over the years.