das Herzstück
centerpiece
The central, most important, or most valuable part of something. It is the core around which everything else revolves.
Der Motor ist das Herzstück dieses Autos.
The engine is the centerpiece of this car.

centerpiece / heart
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centerpiece
The central, most important, or most valuable part of something. It is the core around which everything else revolves.
Der Motor ist das Herzstück dieses Autos.
The engine is the centerpiece of this car.

The word is made up of 'Herz' (heart) and 'Stück' (piece). Just as the heart is the most important muscle in the body, 'Herzstück' (centerpiece/heart) describes the most important, central part of something.
Diese Maschine ist das Herzstück unserer Produktion.
This machine is the centerpiece of our production.
To say what something is the centerpiece of, German usually uses the genitive or the preposition 'von' (of/from). The genitive construction often sounds a bit more formal.
Der alte Marktplatz ist das Herzstück der Stadt.
The old market square is the heart of the city.
In its figurative meaning, 'Herzstück' (centerpiece) is often used for the core of a collection, a company, an exhibition, or a strategy.
Das teuerste Gemälde bildet das Herzstück der Ausstellung.
The most expensive painting forms the centerpiece of the exhibition.
You can recognize the literal meaning 'heart of an animal' from the context. It is used almost only in cooking, in recipes, or at the butcher's.
Auf der Speisekarte stand ein Ragout vom Herzstück.
The menu featured a ragout made from heart meat.
heart
'das Herz' and 'das Herzstück' can both mean the most important or central part of something. 'das Herz' is more figurative and can describe the inner or most important area. 'das Herzstück' is more precise and emphasizes: this part is the core around which everything revolves. The words can be confused because both can mean more than just the organ. In many factual texts, 'Herzstück' sounds more natural when you mean the most important part of a project, plan, or device. 'Herz' fits better in figurative, more general phrasing.

Das Herzstück der neuen App ist ein einfacher Plan zum Vokabellernen.
The centerpiece of the new app is a simple plan for learning vocabulary.
Der kleine Platz ist das Herz der Altstadt.
The small square is the heart of the old town.