What is the greatest challenge facing people in Turkey as a result in its diversity?

Turkey has a largely homogeneous population in that the majority of the population is Sunni Muslim of Turkish origin. However, there are other ethnic and religious groups within Turkey such as the Kurds and also Shi'a Muslims. The greatest challenge to Turkey due to its internal diversity is the threat of secession and also issues related to national security posed by the Kurdish population. Another major issue today in Turkey is the presence of Syrian refugees and also fighters involved in the Syrian conflict which pose national security threats as well.