I have just created aquick node setup for the animation with Animations Nodes Addon
Basically you put a MBall plane as suggested on the previous answer. Then you pick a MBall and duplicate it wit the instancer node. Then you create a loop with those instance to perform some procedural operations.
Balls are scattered on X and Y via the Randomize vector. To animate them on the Z axis we just use a sine function that is feeded with the frame number. To offset the animation I use the index factor of the loop.
A random number is used to give some sort of random scale to the metaballs.