Monitoring particular variables during a simulation run can be very helpful. The Histogram atom contains such functionality.
First, connect the Histogram to the atom to be monitored and choose a variable to monitor.
Secondly, identify the classes to be shown in your diagram. This can easily be done by using segment generating rules or one by one.
Next, generate a (predefined) color for each class resulting in nice visualization.
Finally, define the start value and class size. In order to get a correct interpretation of the results, these values should correspond with the segments you created.
Important: say v is a class value and s is the class size, then the class contains all scores in (v-s, v]
Tip: Out of range scores: ignore the score or add it to the highest/lowest segment.
Good luck!