Your bitcoins are stored in addresses in the blockchain. This way, your Bitcoin transactions and everyone’s transactions are stored in every full-node in the Bitcoin network. The blockchain is an ever-growing database of transaction information that is sent to all nodes of the Bitcoin network. When you make a transaction, this transaction is distributed over the network and, assuming the transaction is valid, will be included in the next block. When you initiate a transaction, all previous transactions to or from that address are analyzed and a balance is calculated. If your transaction exceeds this available balance, it will be rejected by the network and will not be included in a block. It is also important to note that technically, the blockchain does not actually store coins, it stores the transaction information only. The bitcoins themselves are not isolated objects that require storage.