From a Nest and Google press release:
Google has confirmed in a press release that it is acquiring Nest Labs, the company behind Nest smart thermostats and fire alarms started by Tony Fadell. Earlier reports were quickly confirmed along with the transaction price of $3.2 billion in cash in an official announcement posted on the companys Investor website. In the statement, Google said that Fadell will be staying on board as a Google employee and continuing to run Nest.
Google had already invested in the company through its Google Ventures arm, but the purchase means Nest will officially become a part of Google. In its statement announcing the acquisition, Google noted that Nest will continue its own distinct brand identity and that Fadell will continue to run the company.