It’s scratch your head time! :)

I saw this on Facebook I think!  You have groups of  1, 2, 3 and 4 pens.  (Colour is immaterial.  

How do you change it to reverse that to groups of 4, 3, 2, and 1 pens.  BUT you can only move one pen!

Tigger is puzzled. Can you help him? 
Answer tomorrow!