1. Open EXCEL, and select the "SmartArt" tool in the "Insert" option in the menu bar, as shown in the following figure, step 1 and step;

2. In the pop-up dialog box, as shown in Step 3 below, select "Hierarchy", and then click Step 4 to select the required tree diagram;

3. Choose a tree diagram at will, and the following tree diagram will pop up. You can change the text in the diagram to the required content;

4. Change the shape of the tree diagram: select any tree diagram unit that needs to be changed, right click, and select "Change Shape" in the pop-up menu to change the tree diagram unit into the required shape, as shown in steps 5 and 6 below, and the change effect is shown in "quadratic C" below;

5. Add units of the tree diagram: select any unit of the tree diagram that needs to be changed, right-click and select "Add Shape" in the pop-up menu to add units at the front, back, top and bottom of the tree diagram, as shown in steps 7 and 8 below;

The change effect is shown in the following figure "Level 2 C", in which the original cell shape will be moved down one level after selecting the option of "Add shape above", as shown in the following figure;