# Step 6: Building on the accepted block

As indication of their **acceptance of a block as the first valid block (contains correct proof-of-work and a set of transactions that are all valid and spend unspent coins)**, nodes will proceed to build the chain on top of it.

This is the process by which **the longest valid chain of proof-of-work is extended** and represents the collective agreement of the majority of hashpower on the network.

#### Validation Criteria

* All transactions must be valid and adhere to the network's rules.
* Nodes must ensure that they have all necessary information to validate a block efficiently.


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