[header] How to make a millipede habitat [title] Select the right size container. [step] A glass or plexiglas aquarium is ideal for housing millipedes. You can find one of these in a pet store. 
Such a tank will allow you to easily observe the millipedes and control the lighting. Plexiglas (hardened transparent plastic) will be lighter in weight, so this may be the best choice if you plan to take your millipedes along with you now and then.