Early on, the Ethereum network was extremely congested, and transaction fees were exorbitant. In 2017, Joseph Poon and Vitalik Buterin jointly proposed the Plasma scaling solution—simply put, a layered "chain within a chain" structure that moves most transaction computation and data processing from the main chain to child chains. This can increase throughput to nearly unlimited levels.

**How does it work?**

The idea behind Plasma is actually quite simple. You create multiple independent child chains on the main chain, each equipped with its own block producers and consensus mechanism (which can be PoS, PoA, etc.). Users lock assets (ETH or ERC-20 tokens) from the main chain into the child chains, enabling fast and cheap transactions on these chains. These transactions are confirmed quickly on the child chains, and then the child chains periodically (every few minutes or hours) submit a compressed hash of a batch of transactions—known as the "state root" or "block header"—back to the main chain as cryptographic proof to verify the validity of the child chain's state.

**How is security ensured?**

The security model of Plasma primarily relies on an economic game mechanism: fraud proofs. The main chain acts as the ultimate security layer. If a malicious operator on a child chain attempts to steal user funds or tamper with transaction records, any honest participant can submit a fraud proof to expose this. This design makes malicious behavior costly for operators, thereby ensuring the system's security from an economic perspective.