Multilevel column header for DataGrid in WPF

Question

I have a DataGrid which needs to look like this:

As you c

Answer 1

    
                                
                                    
                                        
                                            
                                                EXPERIMENT 1
                                                
                                                
                                                    MODE 1
                                                    
                                                    MODE 2
                                                
                                                
                                                
                                                    VALUE 1
                                                    
                                                    VALUE 2
                                                    
                                                    VALUE 1
                                                    
                                                    VALUE 2
                                                
                                            
                                        
                                        
                                            
                                                
                                                    
                                                    
                                                    
                                                    
                                                
                                            
                                        
                                    
                                    
                                        
                                            
                                                EXPERIMENT 2
                                                
                                                
                                                    MODE 1
                                                    
                                                    MODE 2
                                                
                                                
                                                
                                                    VALUE 1
                                                    
                                                    VALUE 2
                                                    
                                                    VALUE 1
                                                    
                                                    VALUE 2