Learn Spanish (Latin America): El contorno está siendo delineado en la piel. - The outline is being outlined on the skin.

While the passive with se is much more common in everyday Spanish, the analytical passive (está siendo + past participle) is used when you want to strongly emphasize the ongoing, step-by-step process happening to the subject right now. It is often used in technical, formal, or descriptive contexts, like explaining a tattoo or cosmetic procedure.

Why does delineado end in -o here?

In any analytical passive structure (using a form of ser + past participle), the past participle acts like an adjective and must agree in gender and number with the subject receiving the action. Since el contorno is masculine and singular, delineado takes the masculine singular -o ending.

Could I use sobre la piel instead of en la piel to mean "on the skin"?

Yes, both are grammatically correct and understood. However, en is the most natural and standard preposition in Spanish for something located on a surface or body part. Sobre tends to emphasize being physically on top of or draped over something, which is less fitting for a line drawn directly onto the skin.

Do native speakers actually use estar siendo + past participle in normal casual conversation?