Skin

Skins are graphic files in The Sims and The Sims 2 which are used to represent the head, body and clothing of a Sim, but how they work in the two games is somewhat different. The wide availability of third-party skins has unquestionably contributed to the high visibility of the series.

The Sims
Skins in the original Sims are comprised of two parts per sim: a head and a body. Both are simple bitmap images, numbered to correspond with the mesh file which gives them the desired shape on the sim. Each image file is that Sim's entire body, including skin (there are 3 skin tones - light, medium and dark - and it is common for the same outfit to be made in all 3 tones) and hair. Some skins are accessorised with hats, which have a separate BMP.

Skins are available for different modes of dressing: Everyday, Pajamas, Swimwear and Formal. Some jobs also have "uniform" skins. There are also nude skins for when a Sim is taking a bath or shower (a censor blur appears on top of a naked sim).

Once created, a sim's appearance is not editable from within the game, except for their clothes. Some third-party utilities let players change a sim's appearance.

The Sims 2
With the advent of the full 3d environment in The Sims 2 (See Comparison between The Sims and The Sims 2), skins become more complex. Skins are still in BMP format but are now contained in a "package" file, which can be extracted (and compiled) with the included Body Shop tool.

A sim's body is now separate from their clothing, and there are now 4 basic skin tones (light, medium-light, medium-dark and dark) with each skin tone's graphic files being divided by age and gender. This means it is now possible to create distinguishing marks such as tattoos that are unique to a sim, although in practice this is not economical for drive space (there is speculation tattoos will be a feature of a future expansion pack.). Hair is also separate, with different colours and styles, and eye colour can also be set. These traits are carried in a sim's genetics, and passed on to their children.

Sims can change their appearance through a mirror. Hair colour, hairstyle, facial hair (male teens and older only) make-up, glasses and face paint can be changed.

Clothing has also undergone changes. Not only is there far more detail, but when wearing their Everyday clothes the top half of a Sim's outfit can be made separate from the bottom half, or simply be one piece. The modes of dressing are Everyday, PJs, Underwear, Swimwear, Formal and Workout Gear. Pregnant Sims will wear maternity clothes, although this can't be assigned by players.

New outfits
In both games, new outfits can be bought at community lots. (in The Sims, there's no need to buy new Everyday outfits, as all wardrobes already contain all of them)