Here are my thoughts on what's going on.
The citizenry of the U.K. voted yesterday to leave the European Union. The seeds of the EU were planted in 1973. It became more formalized with the Euro currency introduction in 1999 and the fall of the Berlin Wall a decade before that. This ushered in a period of more free trade and more freedom of movement across borders. These open borders have culminated in massive migrations out of areas of conflict, such as Syria.
These resulting refugee migrations have strained the cultures and social fabrics of these European countries who have strong regional cultural ties. Add in to the mix Muslim mores that conflict greatly with western culture. Throw in a few demonstrations and religiously inspired stabbings and rapes and you can see the political backlash ripen.
So the issue with today's markets is that speculation has been building that this election would go the other way and stability would reign. A poll last week confirmed a close race with leanings toward staying in the EU. The opposite result is what occurred and markets exhale.