A minor but really attractive enhancement to any model is the incorporation of illumination into the base. Obviously, a pre-requisite is that you will want a base for your molecular model or crystal structure model, but the incorporation of lighting in the base works best with models that are made using transparent coloured balls that reflect and refract the light to amazing effect.
Illumination in the base of a crystal structure model
The power source can be either powered by replaceable single-use/rechargeable AAA batteries, fixed rechargeable Lithium ion batteries with a recharging socket in the base, or they can be powered with an external power source. All of the wiring is contained in the base in all cases.
Illuminated model of an atom
The cheapest option is the external source, but this also makes the least flexible position for the model, as it has to be close to its power source. The use of AAA battery-powered units allows the model to be much more portable, but is slightly fiddly to recharge or replace batteries. Finally, whilst a slightly more expensive option, the inclusion of a lithium-ion battery and charge control circuit in the base allows the battery to be recharged via a USB cable.