In the first article of this series, we told Cardano and Midnight: Origin Stories and described Midnight as Cardano's first production "partner chain." It's a tidy phrase, but it raises an obvious question: what exactly is a partner chain? The blockchain world is already crowded with words for how networks connect to one another — sidechains, rollups, layer-2s, bridges. Adding another term only helps if it means something genuinely different. As it turns out, it does. Understanding what a partner chain is, and what it isn't, is the key to understanding how Cardano and Midnight fit together.

A Quick Tour of How Blockchains Connect

To see what makes a partner chain distinct, it helps to remember how other connected chains work.

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