Square is a mobile payment system that allows individuals and small businesses to accept credit card payments through a small card reader that plugs into a smartphone or tablet. Founded in 2009 by Jack Dorsey, Square has experienced rapid growth, processing over $2-10 million per week in transactions after signing up over 100,000 users in its first few months. The free Square reader allows easy credit card processing without a traditional merchant account by swiping cards on the smartphone which are then charged a 2.75% fee per transaction. Square has improved over time based on user feedback and aims to process $1 billion in transactions in 2011 while exploring future expansion opportunities.