I find a smoothie often hits the spot when I'm having one of those "I'm hungry but I don't know what I want" days. I believe when that feeling happens it's because my body needs some sort of vitamin or mineral or something else essential that I have not been supplying it with properly.
I haven't ventured too far into the world of "green smoothies" yet. Spinach in a fruit smoothie is about as adventurous as I have been, but the diagram below is informative for the more daring out there.
And remember ... although properly made smoothies can be delicious and nutritious, depending on what you add to them ... they can, very sneakily (is that a real word?) become calorie laden as well. Choose ingredients wisely!
I found these two graphics on Pinterest and happily note that the originating websites are on the bottom of each. Thanks to the talented people who create these so that the rest of us (not so talented) people can share them.