How can I create a mesmerizing DIY ferrofluid in a bottle?

To create a mesmerizing DIY ferrofluid in a bottle, you will need to mix together oil, a magnetic powder like iron oxide, and a surfactant to prevent clumping. Place the mixture in a clear bottle and add a magnet to manipulate the fluid's patterns. Experiment with different ratiOS and techniques to achieve the desired mesmerizing effect.