Hi Azadeh,
Thanks for your interest in Syncfusion products.
Here is a minimal sample that helps on how to embed a Treeview in ot the cell of grid.Please refer to it.
http://websamples.syncfusion.com/samples/Grid.Windows/Development/GDBG_WF_TreeCellType.zipPlease let me know if this helps.
Regards,
Nisha