🧱 How Does Blockchain Store Data?
Unlike centralized databases, blockchains use a distributed ledger: data is copied across thousands of nodes. For example, Bitcoin's 2024 ledger exceeds 500GB and is synced across 10,000+ nodes. One transaction = recorded everywhere = can't be altered.

📦 What’s in a Block?
Each block contains:

Transaction data (e.g., “You sent me 1 BTC”)

A hash (unique fingerprint)

The previous block’s hash (linking blocks into a chain)
SHA-256 ensures even a tiny change alters the hash, making tampering almost impossible.

🔒 Why Is It Secure?
Decentralization: One node failing doesn't break the system

Immutability: To alter data, you’d need 51% of the network—costing billions

Transparency: All data is public; you can check 10-year-old transactions

🌐 Beyond Money
DeFi: Loan records

NFTs: Ownership of digital assets

Supply chains: Walmart tracks food origin in 2.2 seconds
In the future: IDs, votes, and more on-chain.