3. How do migrants get to Europe?
The International Organization for Migration (IOM) estimates that more than 1,011,700 migrants arrived by sea in 2015, and almost 34,900 by land.
The EU's external border force, Frontex, monitors the different routes migrants use and numbers arriving at Europe's borders and put the figure crossing into Europe in 2015 at more than 1,800,000.
Most of those heading for Greece take the relatively short voyage from Turkey to the islands of Kos, Chios, Lesvos and Samos - often in flimsy rubber dinghies or small wooden boats.