This visualization is found as a static image in most physics textbooks. Despite its simplicity it is a good model for the magnetization of ferromagnetic material. Adjust the strength of an external magnetic field from zero in either direction.
A block of unmagnetized ferromagnetic material (e.g., iron) is shown. The magnetic domains are represented by small magnets in arbitrary orientations that cancel out a magnetic effect. An external magnetic field increases the number of domains that have the same orientation as the external field. This is visualized by a growing number of the small magnets becoming equally directed.