the majority) are not required to commit any economic resources beyond a consumer-grade computer with 1-2 TB of available storage and an internet connection. This category requires committing economic resources (such as GPU hash power in proof-of-work or staked ETH in proof-of-stake) in exchange for the ability to occasionally propose the next block and earn protocol rewards. This category includes mining nodes under proof-of-work (PoW) and validator nodes under proof-of-stake (PoS). Nodes that propose blocks are only a small number of the total nodes on Ethereum. There are two types of Ethereum nodes: nodes that can propose blocks and nodes that don't. As Mainnet merged with the Beacon Chain, it also merged the entire transactional history of Ethereum. Instead, the proof-of-stake validators have adopted this role and are now responsible for processing the validity of all transactions and proposing blocks. Mining is no longer the means of producing valid blocks. The Merge represented the official switch to using the Beacon Chain as the engine of block production. After The Merge, the Beacon Chain became the consensus engine for all network data, including execution layer transactions and account balances. After extensive testing, it became time for the Beacon Chain to reach consensus on real world data.

Instead, it was reaching consensus on its own state by agreeing on active validators and their account balances. The Beacon Chain was not originally processing Mainnet transactions. On December 1, 2020, the Beacon Chain was created as a separate blockchain to Mainnet, running in parallel. Throughout Ethereum's history, developers prepared for an eventual transition away from proof-of-work to proof-of-stake. This allowed the Ethereum blockchain we're all used to to come into existence in July 2015 with all its familiar features-transactions, smart contracts, accounts, etc. Proof-of-work secured Ethereum Mainnet from genesis until The Merge. This merged the new, more efficient engine into the existing ship enabling it to put in some serious lightyears and take on the universe.

After significant testing, it became time to hot-swap the new engine for the old one mid-flight. With the Beacon Chain, the community built a new engine and a hardened hull.

Imagine Ethereum is a spaceship that launched before it was quite ready for an interstellar voyage. The Merge was when these two systems finally came together, and proof-of-work was permanently replaced by proof-of-stake. Ethereum Mainnet - with all it's accounts, balances, smart contracts, and blockchain state - continued to be secured by proof-of-work, even while the Beacon Chain ran in parallel using proof-of-stake. Initially, the Beacon Chain shipped separately from Mainnet. Ethereum State: transactions, apps, contracts, balances ⛏ Proof-of-work 🌱 Proof-of-stake 🚀 Beacon Chain 🐼 The Merge 🌳 Sharding

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