Starting now, you have the ability, if you wish, to architect and upload your own genesis block to the Ethereum private blockchain network you created for your organization.
First off what is a genesis block?
A genesis block is the first block of a blockchain. Modern versions of Bitcoin number it as block 0, though very early versions counted it as block 1. The genesis block is almost always hardcoded into the software of the applications that utilize its blockchain. It is a special case in that it does not reference a previous block.
So why would I want/need to build my own?
The genesis block is the first block in an Ethereum blockchain. By providing a custom genesis block configuration you can set the properties of the blockchain such as setting the chain id, initial difficulty, block gas limit, pre-funded accounts, etc.
It also allows you to replicate the behavior of the Ethereum main- or testnet by creating a blockchain with similar properties.