Update 3 3 open layer

3-3-open-layer.md

@@ -4,7 +4,7 @@
 ##### Adding layers
 After opening data files, you can add layers to the 3D-image in the **Rendering Pane** as follows:
 
-1.  In **Menu Bar**, choose *Layer* category.
+1.  In *Menu Category*, choose *Layer* category.
 1.  In *Add Layer* panel, click the corresponding button with the layer that you want to add.
 
     ![](img/3-3-1-add-layer.png)
@@ -14,8 +14,11 @@ After opening data files, you can add layers to the 3D-image in the **Rendering
     ![](img/3-3-1-edit-layer.png)
 
  
+After adding a layer, the program adds one more category corresponding to added layer in **Menu Category**, such as *Horizontal Plane* category. The name of the added category and its ribbon are displayed differently with different added layer.
+
+![](img/3-3-1-add-category.png)
+
 
- 
 
 ##### Viewing data
 To display the data of a variable on the current layer, on the **Variables Pane**, you can select that variable in the list and: