Exodus: Behind the scenes
More than a million migrants crossed the Mediterranean in 2015 - often on overcrowded boats - and many went on to trek hundreds of kilometres to northern Europe.
Some agreed to film their journeys for the BBC and recorded dramatic footage - from the sinking of a rubber dinghy, to a three-day trip in the back of a lorry destined for the UK.
It took a year to make Exodus: Our Journey To Europe, which was shown on BBC Two this week. This is how it was done.
Video editor: Trace Taylor