In the simplest sense, a smart object is any physical object that includes a unique identifier that can track information about the object. More complex smart objects may contain sensors and computers in addition to a unique identifier, but the sensor and the computer may also be separate tools that interact with a tagged object that has no electronic components. Radio-frequency identification (RFID) tags and quick response (QR) codes can be attached to everyday things to turn them into smart objects, as can other means of identification like those that make smartcards work. More sophisticated smart objects may look like blocks but contain computers and the ability to sense position, proximity to other smart objects, light, heat, color, and so on.