Revelers around the globe bid farewell on Monday to a year filled with challenges to many of the world's most basic institutions, including politics, trade, alliances and religion. 

Fireworks, spiritual services and political addresses abounded to mark the transition. 

As the world celebrates, many are wondering whether the turmoil witnessed in 2018 will spill over into the next.

Here is a look at how people are ushering in 2019: