Two explosions shook Zaventem Airport and another ripped through the Maelbeek metro station in Brussels on Tuesday morning, killing at least 28 people and injuring dozens more.
As a way to show support, people can now filter their Facebook photos with an overlay of black, yellow, and red - the colors of the Belgian flag.
It's similar to the French flag overlay option that Facebook gave users following the attacks on Paris in November 2015.
While there is no official Facebook app for changing your profile in support of Brussels yet, there is still a way to do it using a website called Rainbow Filter.
Here's how it works.