Expression is a collectible used for upgrading. (You can use Special:WhatLinksHere/Expression to find the list of buildings that use this collectible for upgrade.)
This collectible was issued with the limited-time Academia Nuts-themed quests starting on the 12th of October 2012.
You can carry only 8 pieces of Expression in your inventory.
This rare collectible can only be obtained by sending your registered University Students to work at Attractions.