The story behind Einstein's riddle is that Albert Einstein created it in the late 1800s, and claimed that 98% of the world population couldn't solve it. I am not sure of the true origin, but I have seen this one floating around the internet, and it is a good brain exercise.

Here it is:
- In a street there are five houses, painted five different colors.
- In each house lives a person of different nationality
- These five homeowners each drink a different kind of beverage, smoke different brand of cigar and keep a different pet.

Einstein's riddle is: Who owns the fish?

Necessary clues:
1. The British man lives in a red house.
2. The Swedish man keeps dogs as pets.
3. The Danish man drinks tea.
4. The Green house is next to, and on the left of the White house.
5. The owner of the Green house drinks coffee.
6. The person who smokes Pall Mall rears birds.
7. The owner of the Yellow house smokes Dunhill.
8. The man living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to the one who keeps cats.
11. The man who keeps horses lives next to the man who smokes Dunhill.
12. The man who smokes Blue Master drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The Blends smoker lives next to the one who drinks water.