A type of censorship used in non-pornographic anime and manga. Instead of pixelating or covering nipples or genitals, they're simply not drawn.
There are laws in Japan against showing genitals in entertainment media, whether it's anime, a TV show or even a pornographic film. Nipples, while not falling under any of these laws, aren't suitable in anime or manga aimed at young audiences. Because of this, nipples are usually censored and genitals always are. The "Anime Anatomy" method (also known as the Barbie Doll method) is to simply omit drawing them altogether, leaving characters without those particular anatomical features.
The Barbie Doll method is often used if a scene features nudity but is intended to be tasteful or viewed by a young audience. Because eroticism is not the primary intended focus of such scenes, the concept of "less is more" is a popular choice over other censoring methods such as mosaic pixelation (a staple of hentai), which can be unsightly and distracting, or convenient censorship.
Nipples on men usually aren't shown in anime or manga, though they are actually considered acceptable and don't need to be censored. In some cases, male nipples are visible only in close-up shots.
This method is more popular with anime shows that will never be shown in any kind of "uncensored" form. Anime aimed at older audiences tend to use the convenient censorship method since nipples are initially drawn and it becomes easier to just obscure them with objects, light beams or shadows for television broadcast. The convenient censorship is then not included on home releases.