The Blockchain Demo project by Sean Han is an interactive website which teaches you how a Blockchain works in an intuitive, bite-sized fashion.
Working through the tutorial you start with the genesis block to which you slowly add more data and hence blocks to the Blockchain. You'll explore why the chain forms a tamper-proof ledger, how a Peer-to-Peer network is formed to exchange blocks and how consensus is reached within such network based on protocols like Proof-of-Work.
With every step of the way you can look into the code underlying the implementation. The full source code can be found at GitHub.
- Sean Han