So this poster is an advertisement for a children's book called The Inner Values Of Tanya's Bra.
The poster is inside every copy of the book.
On Wednesday, a German Twitter account for a campaign called Who Needs Feminism posted a picture of the poster.
"#IchbraucheFeminismus, damit solche Werbung nicht mehr in Schulen aufgehängt werden dürfen!" (Lina)
The tweet reads: "I need feminism, so that such advertising won't be shown in schools!"
The campaign told BuzzFeed Germany it had seen the poster hanging in a high school in Mecklenburg-Vorpommern.
In the poster, male and female body parts are compared, apparently through a teenage boy's eyes.
And the girl's breast is described as a "verwirrmodul" – literally a "puzzlement module".
While the girl's feet are described as a "high heels-holder".
According to the this trailer for the book, it tells the story of a 13-year-old boy named Ben, who's in love with a girl named Tanja.
The book was written by "Alex Haas", which is actually the pen name of this author: Jutta Wilke.
The poster has trended all over German social media, with a huge number of people complaining about it.
Lieber #oetingerverlag das ist ja wohl das aller letzte - so ein Frauenbild wollt ihr zeigen? https://t.co/lXKUYS0OKA
This person asks if this is how women want to be seen.
This person on Facebook says "Astrid LIndgren [a famous Swedish female author] would be thrilled".
They add: "This has nothing to do with understanding of pubescent boys, it's just sexism. And with the same 'excuse', which the advertising industry uses: is it funny, irreverent, ironic... Such sexual images are humiliating for girls and boys."
This person says they won't be buying books from Oetinger (the publishing group) again.
People have also been drawing alternative illustrations.
Hallo Oetinger-Verlag, ich hab da mal was richtig gestellt zu Euren Ansichten, ne? Danke, tschöss!
The Oetinger publishing group defended the poster on Facebook, saying it was not meant to be taken seriously.
The publisher said it was not supposed to be "a serious representation of gender characteristics", but was supposed to show how "prejudice is widespread among young people in puberty."
Doris Janhsen, the managing director of Oetinger publishing house, told BuzzFeed News the book "plays with gender stereotypes".
She said the book "translates the embarrassing aberrations of the protagonists in the picture...really only one response is possible." She said that "really only one response" was possible to the "underlying gender stereotypes...laughter and humour is known to be the best weapon."