From the Hotspots Browser right click a function and select Show Callers/Callees.

This will open the Invocations Browser.

The Invocations Browser is focused on one function at a time, and shows a combination of all the sampled call stacks that include that function.
The Invocations Browser is useful in determining what call paths at runtime result in calls to the function under focus. There may be many possible call paths shown in the Call Hierarchy view, which is populated by looking at the static structure of the application's source code, but only the paths that actually got sampled at runtime are shown in the Invocations Browser.
It may be the case that the footprint of a "hot" function can be reduced by changing the program so that the function is called less often. The call paths shown in the Invocations Browser make a good starting point when looking for places to reduce how often the function is called.
Keep in mind that function inlining may result in functions going "missing" from the Invocations Browser. For example if function A calls function B, and function B calls function C, and B is inlined into A, then the Invocations Browser would only show the direct call from A to C that actually occurred at runtime.
The Invocations Browser is most useful with C/C++ applications. With Java applications it will show calls in JNI and the JVM itself but not in your Java code. COBOL applications will show calls from your procedures to the COBOL runtime or other procedures, but will not show flow within a procedure.
To view the source code for a function, right click it and select Open Source. (Double clicking the function has the same effect.)

Right click a function and select Graph the selected function to open a second Invocations Browser with that function under focus.

Right click a function and select Identify the selected function to highlight all the call paths in the graph that include that function.

All of the instances of the selected function become highlighted as well as all the paths that lead to it.

To clear the highlighting right click anywhere in the browser and select Clear function identifiers.
