Nested grids in Extjs 4

I need to implement a nested grid 开发者_运维知识库functionality in extjs 4. I searched online and it seems like Rowexpander from http://dev.sencha.com/deploy/ext-4.0.2/examples/grid/grid-plugins.html is the way to go. My issue is that I can't get it to work to display another grid (displaying text works fine).

I need to make it look like this: http://examples.ext.net/#/GridPanel/RowExpander/MultiLevel_GridPanel/ using pure extjs 4.

Can someone point me in the right direction?

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In ext3 I used the rowexpander and embedded a grid, but later discovered odd IE issues when further enhancing it with things like rowactions, pagination, scrolling on the nested grid, etc. It also adds visual complexity vs a layout where you have 1 grid above another grid. You click a row in the upper grid and it loads the lower grid for the "nested" data related to that row. Obviously that pattern only works for a single nesting. If you need it nested further, you really want a tree and I would use this:

http://dev.sencha.com/deploy/ext-4.0.2/examples/tree/treegrid.html