What process creates sister chromatids which are genetically different

I'm not really sure and i need an explanation and illustration for my answer. If you could provide the explanation or the answer, i'm sure i could find the illustration.

Crossing over during Prophase I.

In meiosis I homologous chromosomes line up at the metaphase plate. Basically two sets of sister chromatids line up side by side. The genetic information of half the sister chromatid from one set can be exchanged with genetic information from half the sister chromatid of the other set.