Page: Roblox Wiki, when you go under API.
http://wiki.roblox.com/index.php?title=API:Class_reference
According to the page in the third paragraph it says:
If you are looking for information on undocumented classes, one of your best resources is the Object Browser pane (under the Help menu in Roblox Studio). Alternatively, you could look through the API dump itself.
It says it could be found under the Help Menu in studio, however in studio this is what it shows:
It being under the Tutorials button, under view.
I am not sure if this is important or not, but just wanted to make sure since it could mislead some people into trying to look around all over the place for the object browser since there is no place that directly says “Help” on the header.
(Could possibly be more descriptive as well, such as saying “In studio under View, and below Tutorials will be Object Browser” or something like that.)