The Block lattice is a type of Directed Acyclic Graph (DAG) consensus mechanism that was first introduced and described in 2014 in the the Nano cryptocurrency's white paper.
The block lattice consensus mechanism provides one blockchain for every user account. Each account is controlled by a unique private key, and each account is replicated to all peers across the block lattice network. The block lattice makes other consensus mechanisms such as Proof-of-Work and Proof-of-Stake unnecessary because each user has authoritative control over their account and transactions.
The block lattice tracks each users account balance and not their transaction amounts, which keeps the size of each block lattice small in comparison to blockchain based systems that track each transaction on their networks. Another unique feature of the block lattice making it different from blockchains is that each user has full control over their own individual blockchain, this gives the ability to update their blockchain asynchronously to the rest of the block lattice network. Asynchronous updating of each users account using block lattice architecture creates multiple non-shared asynchronous ledgers operating on the network instead of the shared global ledgers of blockchain based projects such as Bitcoin.