Feature in Feature, as the name suggests, refers to a nested bonus structure of a 'feature within a feature'. It's a method where the result of a triggered feature (e.g., a mystery symbol) is not just a simple symbol transformation or a payout, but a direct link to a new, deeper bonus feature. Its goal is to go beyond simple anticipation, creating a 'chain reaction of expectations' like "Will this lead to an even better feature?", thereby maximizing the game's depth and unpredictability.