Erik Murphy-Chutorian posted on Google Plus about adding emotions to your Photos.
read the post here
Earlier I thought it is an April Fool Joke but I tried and it is working. it is adding the emotions according to the face expressions.
to add this
simply open one of your pictures in the lightbox, and click the “Add emotion” button at the top left of the screen. Clicking again the button will remove emotions from the photos.
try it. and check more photos here