In order to dive in deep and view how code functions it is not a good idea to put a breakpoint and try viewing it through that. .net installs some samples with it in your installation directory as shown below:

It is inside C:\Program Files (x86)\Microsoft Visual Studio 9.0\Samples\1033

Now we have to click on csharp samples and then on linq samples and then expressiontreevisualizer directory. Now extract it to desktop and open the solution file.

Build the solution and navigate to Bin>Debug directory inside expressiontreevisualizer and look for a dll named ExpressionTreeVisualizer.dll.

Now navigate to Visualizers folder inside my documents->Visual studio 2008 as: 

And move the dll to the visualizers folder. Now stop and restart your visual studio 2008

Now write a linq query and fetch the expression as shown below:

Now click on the visualization sign from the code and you will see the tree as follows: 

In the image above we can see several expressions and an expression tree. This whole information is passed on to .net compiler which in turn converts this into a SQL query and fetches data from database.