Bitcoin is a cryptocurrency invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto and started in 2009 when its implementation was released as open-source software.Bitcoin has been praised and criticized. Critics noted its use in illegal transactions, the large amount of electricity used by miners, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble. Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin. The unit of account of the bitcoin system is a bitcoin. Ticker symbols used to represent bitcoin are BTC and XBT. Its Unicode character is ₿. Small amounts of bitcoin used as alternative units are millibitcoin (mBTC), and satoshi (sat). Named in homage to bitcoin’s creator, a satoshi is the smallest amount within bitcoin representing 0.00000001 bitcoins, one hundred millionth of a bitcoin. A millibitcoin equals 0.001 bitcoins; one thousandth of a bitcoin or 100,000 satoshis. The first and most widely used decentralized ledger currency, with the highest market capitalization.