The Grand National is one of the most famous and toughest horse races in the world - and it takes place this Saturday.
It's a very popular event and 600 million people watch it on TV all over the globe.
The race is part of a three-day race meeting held in Liverpool, with over 150,000 people attending.
Aintree has been the home of the famous Grand National since its first running in 1839.
A version of the race took place in years before this, but 1839 is accepted as the official start of the race as we know it today.
Between 1916-1918 during World War One, the race had to be moved to Gatwick Racecourse. Then, it was called off between 1941-1945 because of the Second World War.
The race has changed since it began.
The courses and fences have been tweaked over the years - not least to make them safer for the horses and jockeys. The starting line was also moved further away from the main stand to help the horses to remain calmer at the beginning.
But throughout the years, it has always remained one of the biggest jump races for horses and riders in the world - and it is currently the longest race in the UK.
The Grand National is held at Aintree Racecourse in Liverpool.
During the three-day event, over 20 different races will take place.
In the biggest race - the Grand National - horses have to complete two laps of the course, covering four-and-a-half miles and jumping 30 fences.
There are 16 different jumps, known as fences, on the National Course. All 16 are jumped during the first lap but on the second lap of the circuit the horses only jump 14 of them - so that makes 30 fences in total for the race.
The fences are different widths and heights, and some of them have different names.
One of the most famous fences is called The Chair, which is the tallest on the course at 5 foot 3 inches. The ground on the landing side is higher than the side the horses take off from, and there's also a six-foot ditch that horses have to jump over before the fence. Crumbs!
Fortunately, The Chair is one of the two fences that riders only have to go over once, rather than twice like most of the others.
The Canal Turn and Becher's Brook are two other extremely difficult fences.
At Becher's Brook, the landing side of the fence is 10 inches lower than the take-off side. According to the race's official website, jockeys have compared it to "jumping off the edge of the world".
Some horses actually refuse to jump The Canal Turn, which can mean they get in the way of other riders.
In the past, loose horses used to sometimes continue straight ahead here after the jump - instead of turning the corner on the course - and end up in the Leeds and Liverpool Canal!
Campaigners and animal rights charities have often complained that the Grand National isn't safe for the horses involved and that the race is too dangerous.
In both 2011 and 2012, two horses died racing in the Grand National race itself and charities like the RSPCA say that had to change.
Organisers of the race have made the fences lower and drops shorter to reduce the danger of the race.
They also added new softer plastic centres to the fences in 2013 to make them safer, but many campaigners say more needs to be done.
There have been no fatalities in the Grand National race itself since 2012, but there have been in other races that take part across the three-day event.
Aintree boss John Baker has said they will "never be complacent" about safety, but added that "you can't ever fully remove the risk".
A horse called Red Rum is the only horse to have won the Grand National three times - in 1973, 1974 and 1977. He also came second in 1975 and 1976.
Red Rum died in 1995 at the age of 30 and was buried near the winning post at Aintree.
In 1993, no one won because there was a false start - some riders didn't realise and carried on so the race had to be cancelled!
George Stevens is the most successful jockey in Grand National history. He has won the Grand National five times, but given that his final victory came back in 1870, you probably weren't around to remember this!
The fastest time ever the course has ever been completed in was by Mr Frisk in 1990, who covered the four miles and 514 yards of the race in just 8 mins 47.8 secs.
Katie Walsh holds the record for the the highest position that a female jockey has finished in the race. She came third in 2012 on a horse called Seabass.
This year, three female jockeys will start the Grand National - Walsh, Bryony Frost and Rachael Blackmore. Can one of them go further this year? We will have to wait and see!
Because we all love a bit of trivia...
- Prince Edward VII actually owned the 1900 winner Ambush II. Less than a year later, he became King of England!
- Not all horses manage to finish the race - for example, if their rider falls off. The most number to complete the Grand National is a record 23 horses in 1984.
- In 1929, an incredible 66 horses started the race but only two finished in 1928.
- The oldest horse to win the race was Peter Simple. He was 15 years old and won in 1853.
- Five horses have won the race aged only five years old.
- The oldest winning jockey was Dick Saunders in 1982, aged 48.
- Bruce Hobbs had just turned 17 three months before the Grand National when he won in 1938, making him the youngest ever winner.