## The Four Layers of the Blockchain World: From Underlying Protocols to User Applications

Many people have heard that Ethereum is working on Layer2 scaling solutions, but the concepts of Layer0, Layer1, Layer3 are still foggy. Today, let's clarify these four layers in plain language.

### Simple understanding: The complete chain from hardware to application

Imagine a building: the foundation and plumbing are at the bottom, then load-bearing structures, followed by decoration and furniture, and finally the residents' daily life at the top. Blockchain follows this logic—**Layer0 corresponds to the internet hardware infrastructure**, Layer1 is the main blockchain, Layer2 is the acceleration layer, and Layer3 is the application we actually use.

### Layer0: The "Infrastructure" of Blockchain

**Layer0 is the underlying transmission protocol connecting the internet and blockchain.** Simply put, without L0, blockchain cannot run on the existing network.

The L0 layer mainly does three things:

**First, enabling communication between different blockchains.** Cosmos is a typical example; it uses the IBC protocol (Inter-Blockchain Communication) to allow multiple chains to communicate. This means that if an application is built on the same Layer0, it can be used across multiple chains directly, without repeated development.

**Second, speeding up cross-chain transactions.** Using IBC + PoS consensus, transactions between multiple chains can be finalized instantly (i.e., permanently confirmed), making cross-chain transactions fast and cheap.

**Third, pre-installing tools for developers.** Developers don't need to build blockchains from scratch; many basic functions are already pre-set and ready to use.

### Layer1: The "Main Stage" of Blockchain

**Layer1 is what we call the main chain—like Bitcoin, Ethereum.** This layer handles and finalizes all transactions, with consensus mechanisms (PoW, PoS), block times, and transaction finality all implemented here.

L1 faces a classic dilemma: decentralization, security, and scalability are hard to achieve simultaneously. So far, no main chain has perfectly solved these three issues.

### Layer2: The "Accelerator" of Blockchain

**The sole purpose of Layer2 is to improve transaction speed and reduce costs.** It doesn't change the underlying rules of L1 but processes transactions outside L1 and periodically submits the results back to L1.

Concepts like zk rollups and sidechains all fall under Layer2. When you see claims like "transactions 10x faster" or "Gas fees reduced by 90%", they are mostly referring to L2 solutions.

### Layer3: The "Application Window" of Blockchain

**Layer3 is the final application layer—like the app on your phone or the web interface.** The relationship between L3 and L2 is similar to that between L2 and L1.

Some developers believe that even with L2, decentralized exchanges still face issues like throughput limits and high Gas fees. So, they consider working on Layer3—customizing an application layer that communicates with other systems via Layer2. This approach is much cheaper than directly connecting from L1 and easier to implement.

### Key Point

**Current cross-chain channels are inefficient and costly,** so shifting operations between different layers to Layer3 might be a more practical solution. Because a customized L3 interacts via L2 rather than L1, it is inherently much cheaper.

In summary: Layer0 is the foundational protocol enabling chain-to-chain connectivity; Layer1 is the main chain that provides core security; Layer2 is the scaling solution that accelerates transactions; Layer3 is the user-facing interface. These four layers are interconnected, forming the current blockchain ecosystem.