Sharding

At present, every node needs to download all transactions, which is huge. At the rate at which blockchain size is increasing, in the next few years, it will be very difficult to download the whole blockchain and keep it in sync.

If you are familiar with distributed database architecture, you must be familiar with sharding. If not, then sharding is a method of distributing data across multiple computers. Ethereum will implement sharding to partition and distribute the blockchain across nodes.

You can learn more about sharding a blockchain at https://github.com/ethereum/wiki/wiki/Sharding-FAQ.