On Wednesday, Microsoft’s chief of Microsoft AI, Mustafa Suleyman, announced that access to the o1 model would be available to Copilot users “everywhere at no cost.” Access to the model will be provided by Copilot’s “Think Deeper” function, which requires a few seconds to ponder and research an answer and spit out a response. Because the Copilot app on Windows is now just a PWA, or webpage, you can access it by either the Copilot app on Windows or via copilot.microsoft.com. You’ll need to sign in with a Microsoft account.
(The “Think Deeper” control in Copilot is essentially a toggle switch. Just make sure it’s “on,” or highlighted, before you enter your query.)

Think Deeper is essentially a more thoughtful version of Copilot, which recently seems to have trended toward more cursory, shorter replies. Don’t consider it a search engine, however; when asked, Think Deeper noted that its information was current up to October 2023.
Instead, Think Deeper excels at what you might call evergreen research — relating the evaporation cycle to hurricane development, or analysis of a given situation or historical event, for example. Think Deeper will write code and explain it, too: “Write a basic Windows application that can be used to draw a maze based upon the letters of the user’s first name” produced a thorough process to develop the application, generating custom C# source files after several seconds. (I haven’t taken the time to test it out and/or debut it, however.)