Slot machines are currently the most popular casino game in the world and can be played at both land-based casinos and online.  In total, it is estimated that slot machines make up 70% of casino revenue in Las Vegas and Rio.  The huge lobbies and arrays of slot machine players along the floor of most casinos is a testament to this.  In fact, the first thing that usually spots you when you walk into any casino is slot machines and players.

The first even slot machine was invented by Charles Fey in California in 1887.  His machine, called "Liberty Bell" provided a solution to the first gambling machine that could process automatic payouts.

His Liberty Slot machine was the first ever classic "3-reel" slot machine.  It had three reels with a total of five symbols on each reel.  The maximum prize was three Operator Bells aligned on the pay line which dispensed 10 cents.

The simplicity of this machine replaced similar "poker machines" which had too many different variables and payouts to be automated.  For example, with so many different types of poker hands such as pocket kinds, two pair, full house, flush, straight etc it was too difficult to manufacture a machine capable of paying out all these different hands.  This is why Fey's 3-reel slot machine was so successful.

Soon after it became popular, many other manufacturers (including Herbert Mills) produced their own slot machines such as Operator Bell.  These machines were placed a in variety of bars, cigarette stores and barber shops across the country.

More complex slot machines based on poker, which arguably paved the way for modern video slot machines were produced. These poker machines had 5 reels with a total of 50 cards, however because of their complexity prizes usually included free drinks or offers which you had to go to the serviceman to claim as opposed to direct cash payouts.

The first elecromechanical slot machine was invented in 1966 called "Money Honey".  The problem for mechanical slot machines at this time however was that payouts had to be limited because of the higher odds of players winning.  The solution to this problem came in the late 20th century as micro-processing chips and weighted symbols reduced the probability of a winning pay line.  This allowed prizepools and slot machine payouts to be much higher, regularly worth £500 up to £1 million.

In 1994, the first online casinos were born which also provided online slots games.  Nowadays, online slots have far more features included bonus rounds, interactive games, Hold N Spin or Cascade rounds , progressive jackpot games and more.  You can even take part in online slots tournaments online at sites such as Slotastic and All Slots Casino.