QR stands for quick response. There are multiple versions of the QR, including model one, model two, the Micro QR code, IQR, SQRC and the Frame QR.QRs can hold more information than a barcode, so ...

Micro QR code: A smaller version of a traditional QR code for when space is limited. Micro QR codes can vary in size, but the smallest is 11 × 11 modules, encoding up to 21 alphanumeric characters.

Micro mirage: Researchers fabricate the world's smallest QR code using infrared information carrier. by Kaitlyn Landram, Carnegie Mellon University Mechanical Engineering.