What's the reaction here?
$\ce{KI}$ with $\ce{H2O2}$ with a tiny bit of dishwashing liquid. It is a rather violent redox reaction wherein $\ce{H2O2}$ is decomposed to $\ce{H2O}$ and $\ce{O2}$. You can actually see that $\ce{I2}$ is being formed by the brownish-yellowish color in the beginning of the reaction.

There is a lot of information about this reaction. I performed this reaction quite a few times myself for my students. It is a lot of fun. Some people call it making elephant toothpaste. :-)