They have to intertwine, as shown in the following diagram. So during the process of synapses, the point at which our two chromatids intertwine, or overlap, is known as our chiasma. And in this diagram, the chiasma is basically this point here. It's the point at which our two chromatids, this chromatid and this chromatid, basically overlap. Now, because we have four individual chromatids, we have one chromatid, two, three chromatid, four. This entire structure is known as a tetrid.