PIXXO 3D uses a simple liquid simulation to make a melting brain in Blender.

Pixxo 3D Juandre (Jay) Labuschagne shows how he created a melting brain animation in Blender by working with a liquid simulation. The tutorial covers tips and tricks for getting the simulation to behave correctly and not go through some objects in the scene using proxy objects.

Check out this liquid simulation tutorial using MantaFlow, from the Blender Made Easy channel to create a direct fluid simulation and apply bright colors to each particle. The colorful fluid simulation relies on a simple material to handle the effect.