An unabridged collection spotlighting the best hard science fiction stories and novellas published in 2021 by current and emerging masters of the genre, edited by Allan Kaster.- "Light Up the Clouds" by Greg Egan - Inhabitants in the floating forests of a gas giant that orbits a dwarf star launch a glider on an orbital trajectory to investigate unnatural asteroid-like objects that threaten their survival.- "Striding the Blast" by Gregory Feeley - As a form of punishment, a thief is forced by posthumans to race on a set of wings across a cloud-covered Mercury.- "Little Animals" by Nancy Kress - Using entangled quantum effects, a researcher goes back in time and unexpectedly becomes immersed in the life of the daughter of Antonj van Leeuwenhoek.- "Flowers Like Needles" by Derek Kunsken - A metallic crablike creature living on a planet orbiting a pulsar confronts other warriors in its quest for wisdom.- "The Planetbreaker's Son" by Nick Mamatas - Interstellar posthuman emigrants, on a starship the size of a football stadium, grapple with vessel maintenance and family preservation while destroying worlds.- "Paley's Watch" by Anil Menon - Fishermen find a peculiar artifact in the Gulf of Alaska that is older than Earth and models the structure of the universe.- "The Metric" by David Moles - A billion-year-old ship delivers a message to a far-future Earth that could mean the destruction of space and time.- "Ano Nuevo" by Ray Nayler - Listless aliens, resembling oversized plastic garbage bags, suddenly disappear thirty years after arriving on a California beachfront.- "Vaccine Season" by Hannu Rajaniemi - A boy ventures out to an island to inoculate his secluded grandfather with a transmissible vaccine in a post-pandemic.- "Submergence" by Arula Ratnakar - An investigator uncovers the exploitation of an unusual marine sponge while optogenetically accessing the memories of a scientist who died unexpectedly.- "Aptitude" by Cooper Shrivastava- A woman from a slowly dying universe finds herself having to take a rigorous standardized exam after cheating her way into the selection process to become a universe builder.- "The Egg Collectors" by Lavie Tidhar - Two wild ballooners, forced to land during an ice storm, discover humming black eggs melting into the ice of Titan's Ligeia Mare.