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 Künsken - 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.· "Año 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.