Here are some handy "research" tools we use to explore he inner workings of Mac applications:
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its content, like imported symbols, or the control flow graph.
A .nib file is a special type of resource file that you use to store the user interfaces of iOS and Mac apps. A nib file is an Interface Builder document. You use Interface Builder to design the visual parts of your app—such as windows and views—and sometimes to configure nonvisual objects, such as the controller objects that your app uses to manage its windows and views. In effect, as you edit an Interface Builder document, you create an object graph that is then archived when you save the file. When you load the file, the object graph is unarchived.
The NibDecompiler allows you to decompile a nib file so that you can open it in Xcode.
Asset Catalog Tinkerer is an app that lets you open .car files and browse/extract their images.
RSRCManager allows you to explore the contents of .rsrc files.