Today’s SUMS talk is being given by Sean Gardiner. Abstract: When it comes to tessellation, no simple shape is less amenable than the circle. The problem of fitting circles together "nicely" has been investigated under various interpretations, and is still the source of many unsolved questions. This talk will aim to briefly discuss and exemplify several circle packing problems and constructions, from plane-tiling to polygon-filling to Apollonian gaskets.