How do Layer 0-4 work?

In 2021, Ethereum fees were as high as $50 per transfer. Today it's less than $0.01. How come? It's because of the blockchain's multiple layers. Layer 0 connects networks, Layer 2 speeds up transactions, and Layer 4 makes crypto convenient even for your grandmother. Let's break down how it works - without the complicated terms.

Blockchain is not a road, but a multi-layered interchange

Imagine that blockchain is a multi-layer cake. Layer 1 (Bitcoin, Ethereum) is the sponge, the base of the flavor. Layer 2 (Arbitrum, Lightning Network) is the cream that makes the cake more tender. Layer 0 (Polkadot, Cosmos) is a plate on which you can put several cakes at once. And Layer 3 and 4 are the decorations and the fork, without which it is inconvenient to eat.

But metaphors are good, but facts are better. Why can't Bitcoin process more than 7 transactions per second? How did Ethereum reduce commissions 100 times? And why do we need "add-ons" like The Graph? Let's look at it in order.

Layer 0: Why can't blockchains become friends without it?

The problem: 

Blockchains live in isolation.

Transferring tokens from Ethereum to Solana used to be nearly impossible - like sending a letter from one universe to another.

Solution: 

Layer 0 is the "internet for blockchains".

It provides:

1. Cross-chain interoperability (bridges like Axelar).
2. Shared security (Polkadot shares validators with parachains).
3. Development flexibility (Cosmos SDK allows you to build your blockchain in days).

Examples:

• Polkadot is "LEGO for blockchains": projects rent slots to work in its ecosystem.
• Cosmos - "Google Translator" for networks: its IBC protocol connects 50+ blockchains.
• Avalanche Subnets - "private islands" for enterprise solutions.

The future: Layer 0 is blurring boundaries.

Soon we will see a single space where tokens and data flow freely between networks.

Layer 1: why are Bitcoin and Ethereum just the beginning?

The problem: 

The underlying blockchains are slow and expensive. Ethereum cost $50 per USDT transfer before moving to PoS.

Solution: 

Layer 1 is the foundation

Its main challenges:

• Security (PoW in Bitcoin, PoS in Ethereum).
• Decentralization (thousands of nodes).
• Execution of smart contracts (EVM in Ethereum, Solana VM).

Examples:

Bitcoin - "digital gold" where immutability is more important than speed.

Ethereum is the "world computer", the leader of DeFi and NFT.

Solana - "speed train", 50,000 TPS thanks to parallel transactions.

Blockchain Trilemma: 

It is impossible to achieve decentralization, security and scalability at the same time. That's why Layer 2 came into being.

Layer 2: how did Ethereum learn to “breathe”?

The problem:

Core networks are overloaded. $50 commissions are killing micropayments.

Solution:

Layer 2 processes transactions “side-by-side” with L1, then writes the total to the main blockchain.

L2 types:

Rollups (Optimism, Arbitrum) - “batch transfers”, reduce fees by a factor of 10.

ZK-Rollups (zkSync, StarkNet) - “the magic of crypto”, privacy + speed.

Sidechains (Polygon PoS) - “separate roads”, faster but less secure.

Example:

• Lightning Network for Bitcoin allows you to pay for coffee without long confirmations.

Bottom line:

L2s are the “ambulance” for scaling. Without them, DeFi and gaming would not be possible.

Layer 3: Why does blockchain need a “special forces”?

Issue:

Even L2s aren't ideal for narrow tasks - like gaming or private transactions.

Solution:

Layer 3 is all about customization:

dApps (Uniswap, Aave) - run on top of L1/L2.

Infrastructure (The Graph, Chainlink) - “data delivery services”.

Modular blockchains (Celestia) - allow you to assemble the network like a constructor.

Example:

• Immutable X - L3 for NFT games with zero commissions.

Trend:

In the future, L3s will become “virtual worlds” with unique rules.

Layer 4: how did MetaMask and Uniswap conquer the world?

The problem:

Crypto is complicated. The average user won't write code to translate tokens.

Solution:

Layer 4 is about interfaces:

Wallets (MetaMask, Phantom).

Exchanges (Uniswap, dYdX).

Web3 applications (Brave, STEPN).

Chip:

Without L4, cryptocurrency would remain the domain of geeks.

Conclusion: the future is for the “layer cake”

Blockchain is evolving:

🔹 Layer 0 connects networks.

🔹 Layer 1 ensures security.

🔹 Layer 2 speeds up transactions.

🔹 Layer 3 adds specialization.

🔹 Layer 4 makes cryptocurrency accessible.

What's next. The emergence of Layer 5 (quantum stable solutions?) or a complete merger of layers. One thing is clear: layering is not a temporary phenomenon, but the foundation of Web3.