Now let's take a look at what European country leaders think of the Brexit referendum.

German Finance Minister Wolfgang Schaeuble said on Tuesday that the EU needs a change, even if the UK decides to remain in the bloc after Thursday's vote. The finance minister also pointed out that the number of people in EU member states who have doubts about the "EU project" is growing, not only on the fringes of the far right, but also on the left.

French President Francois Hollande said on the same day that he hope the United Kingdom would remain in the union. He wishes that the Brits will make a "wise choice". In his words, "the United Kingdom is part of Europe and the UK bears the value of Europe." If the answer is to leave, every member in the Europe "would face all the consequences of it".

Greek Prime Minister Alexis Tsipras warned on Tuesday about the consequences of Britain leaving the EU. He said that Britain leaving would "bring adverse economic repercussions" for both the European and world economies.