The first one has a dark, futuristic atmosphere:
In the second one, which is definitely my favorite, the artist experimented with smaller amount of ferrofluid which he mixed with other liquids such as milk, soap, alcohol etc.
In the third video he again played around with mixtures of ferrofluid and other liquids. What's really admirable is that no computer software was used for the creation of the patterns but only manipulations with fluid dynamics and magnetism.