Google+ for an undisclosed sum in a deal that closed late Wednesday night. Fridge founder Austin Chang said his four-person team will begin with work with Google+ out of New York, with plans to move next month to move to Google’s (GOOG)  office in Mountain View, California.

Fridge, which had 40,000 unique visitors each month and more than 20,000 groups in its system, allowed users to form instant groups to share pictures, messages and events with specific friends on both desktop computers and mobile devices. Chang said several parties were interested in acquiring the Y-Combinator startup, which raised $800,000, although he did not consider selling to another firm since “Fridge fits perfectly into Google+’s plan.” The companies discussed the deal for two or three months.

Service lets users create and delete groups on the fly

The comparable feature to Fridge on Google+ is called Circles, which allows users to create multiple sets of friends and contacts in order to choose which content to share with each group, instead of being forced to share the same content with everyone. Google plus may benefit from the agility of Fridge, which allowed users to create and delete groups on the fly and easily access them from Web or mobile. In its beta form, Circles requires a more involved and slower process for creating different groups. “Right now, Google+ is asymmetric,” Chang said. “We’re going to help them create shared spaces.”

As Google+ seeks to oust Facebook off the social networking block, it will have to do much to simplify its sharing and group chatting processes, and the acquisition of Fridge sets Google on the path to do so.