Below are  illustrations of two natural fractals. These trees are similar in their structure but  not identical.  Their similar structure contains many small branches and few large ones. The patterns are also similar across the  small detailed and coarser branches emerging from the trees' trunk.  This pattern similarity occurs at different (spatial) scales and is an example of  'statistical similarity.'  We will see an analagous property in eye-movement patterns where there are many small movements (i.e., fixational eye movements) and far fewer large movements (ie., saccades) which maintain their similarity over the course of seconds, minutes and much longer time periods.