The satoshi is not the only subdivision of bitcoin. A millibitcoin is a term for one-thousandth of a bitcoin or 0.001 BTC. A microbitcoin is one-millionth of a bitcoin or 0.000001 BTC. On the Lightning network, it is possible to transact using a unit even smaller than the satoshi. Known as the millisatoshi, it represents one-thousandth of the size of a single satoshi, but this is not usable on the bitcoin network itself.
