How are transactions stored (and recorded) in the Blockchain blocks? Using a concept called a Merkle tree – in this video I break it down in depth with a simple example and show how a SPV node (Simple Payment Verification) node that does not keep a full copy of the blockchain transaction history – just the headers of the blocks – can verify from an adjacent (but not necessarily trusted) full node, which block a transaction is part of just from knowing the MERKLE PATH from the full node.
http://chimera.labs.oreilly.com/books/1234000001802/ch07.html