Viscous fingering

Viscous fingering is when some liquids don't spread out evenly but instead form little fingers. Let's imagine you have a pile of sticky honey on your plate. If you push your finger into it, the honey will move away from your finger and form thin little honey fingers. This is exactly what happens when some liquids move through other liquids.

Imagine you have a pipe with two different liquids in it, one of them is very thick and the other is thin. When these two liquids start to move through the pipe, they don't mix evenly like they should but instead, the thick one forms little fingers that push through the thin one. It's like a maze that gets more and more complicated as the liquids keep moving through the pipe.

This can be a problem when we want to move liquids around efficiently because the thick liquid takes up more space and doesn't move as quickly as it could if it mixed more evenly with the thin one. Scientists are still trying to figure out how to make liquids mix more efficiently and avoid this viscous fingering.