From an overview of Google's 3D tablet project; see this Re/code article for more ATAP details
"ATAP [Google's Advanced Technology and Projects group] is headed by Regina Dugan, former director of the U.S. government’s Defense Advanced Research Projects Agency. It was created as a research lab inside Motorola, the mobile phone maker that Google acquired in 2012.LG to Make a Consumer Version of Google’s 3-D Tablet - Digits - WSJ
Google kept ATAP when it agreed to sell Motorola earlier this year to Lenovo. The decision to retain the group is part of a broader effort by the Internet giant to work on long-term, riskier projects that could turn into new, big businesses in the future.
Project Tango is ATAP’s most-mature project, but the research group has ten other initiatives, Dugan said. They include a “modular” smartphone platform known as Project Ara and a digital tattoo that sticks to the skin, lasts for about five days and can unlock Moto X smartphones made by Motorola."