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React Native is a cross-platform layout engine written in C which implements Flexbox through bindings to the native views (Java Android Views / Objective-C iOS UIKit) All the layout calculations of the various views, texts and images in React-Native are done through yoga, this is basically the last step before our views get displayed on the screen. React Native manages the UI updates through couple of architecture layers that in the end translate how views should be rendered. UIMan is the final piece of the puzzle that actually tells React-native how to render the layout.