Packing Fraction is a companion volume to No Limits, but also a stand-alone anthology. It contains original science fiction short stories, verse, and art commissioned specifically for this project. Each story explores a particular scientific "what if?" premise. For example, the title story by Charles Sheffield explores the consequences of being able to decrease inter-molecular distance, to literally pack more atoms into the same space. The talented authors who contributed to Packing Fraction have succeeded in providing a variety of stories sure to intrigue and stimulate readers.