Have you ever wanted to store an array, hash or object in a database column? Using Active Record and YAML makes this completely painless. To do so, you must specify this with a call to the class method serialize. This makes it possible to store arrays, hashes, and other non-mappable objects without doing any additional work.
You can also specify a class option as the second parameter that‘ll raise an exception if a serialized object is retrieved as a descendant of a class not in the hierarchy.
Nothing new here, but something that can be pretty powerful. Working with people not used to Ruby or ActiveRecord brings back some of the nice “magic” we take for granted on a regular basis. (Samples taken directly from Ruby on Rails API Documentation)