Scent boxes are small, internal modules, used to create a specific, unique scent for the synth. The main purpose for this is for Synths to become more appealing to organics around them. Scent boxes come with different aromas the Synth can choose from. Popular scents are vanilla, sandalwood, citrus, ylang ylang and many others.
A scent box allows the Synth's nanites to synthesize scents from the materials stored within the scent box. Aside from storing the materials needed, scent boxes also store the recipe for their particular scents. Nanites will then use this recipe and the materials stored within the box to synthesize scent molecules. These molecules are transported to the skin via the capillary system, where they then give the Synth their scent. The materials needed for scent synthesis can be restocked by a Synth's metabolism through the consumption of food
Scent boxes are typically exchanged often, since they are small, tend to be affordable, are easy to exchange and can be chosen for different situations. They are optional, meaning that a Synth can simply go without one, which will lead to their scent being mostly neutral. At that point a Synth will mostly smell of the materials their components are made of, if there is any scent to them at all.
The use of scent boxes can be compared to the use of perfumes for organics, except that scent boxes last much longer. One scent box typically can be re-used for years, until it starts to malfunction. Many scents are designer creations, with some brands being more popular or fashionable than others.