Blocks are added to the blockchain through a consensus mechanism, which ensures all network participants agree on the validity of transactions. The process generally follows these steps:

1. A Transaction Occurs

Users initiate a transaction (e.g., sending Bitcoin). The transaction includes:

• Sender & receiver addresses
• Transaction amount
• A digital signature verifying authenticity

2. Transactions Are Grouped into a Block

Pending transactions are collected into a new block by network participants (nodes).

3. Validation Through a Consensus Mechanism

Before a block is added, it must be verified by the network. The two most common methods are:

? Proof of Work (PoW) - Used by Bitcoin

• Miners compete to solve a complex mathematical puzzle.
• The first miner to solve it gets to add the block and earns a reward.
• This process requires significant computational power (energy-intensive).

? Proof of Stake (PoS) - Used by Ethereum 2.0 & Others

• Validators are selected based on how much cryptocurrency they "stake" (lock up).
• The chosen validator confirms transactions and adds the block.
• Staking discourages fraud since validators risk losing their funds if they act dishonestly.

4. The New Block is Linked to the Previous One

• Each block contains a cryptographic hash (unique digital fingerprint) of the previous block.
• This chaining makes it nearly impossible to alter past data without changing all following blocks.

5. Block is Added to the Blockchain & Becomes Immutable

• Once consensus is reached, the block is added permanently.
• The process repeats for new transactions, maintaining an ever-growing blockchain.

Security & Finality

• Decentralization ensures no single entity can alter records.
• Immutability makes transactions irreversible once confirmed.
• Transparency allows anyone to verify transactions on public blockchains.