We are visiting the digital galaxy again - today, as any other day. So grand and immense, expanding by the second. For years, we have roamed here, visiting place after place, yet not seen a percentage of what it has to offer. You would think we would become rather overwhelming at some point. Yet we seldom are. Maybe it's due to the invisible helpers we have by our side, guiding us through these various landscapes and obstacles toward our desired destination. Although many know these guides and interact with them everyday, few know their name: Recommender systems.