Money in the current world has several variations - if we look back into the history we human started trading with shells & later on we started trading cows for our own needs. As times passby we found Gold bars & started using it for trading for goods. We also made the gold bars into the small coins so it can be traded easily based on the counts. later we found the traditional coins with numbers printed on it. As it was found more heavier, we came up with paper money. As we didnt want to get theft or lose our wallet - we moved all our money to money cards (debit). Later innovations ideas forced bank to lend money blindly with mere identification proof which was called Credit card. Then we even not satisified with it, so we moved everything to our handheld device - one can pay using their phones using QR code or BAR Codes. What an Transitions! We will continue evolving with this trend & move towards micro or nano chips that can carry all our debits. Or even we may get things into our identity like Finger Prints or Eye Scanning which can make you carry all your money without holding just nothing!.