Becoming an astronaut is a process that usually takes decades. This book explains what happens during those years and separates the things that matter now from the things young people do not need to worry about yet. Beginning with the work astronauts actually do, the book examines launches, life aboard a space station, spacewalks, emergencies, physical changes caused by weightlessness, teamwork, communication, and the long stretches of training and ground work that make up much of an astronaut’s career. The countdown then moves backward through astronaut candidate training and the selection process. Readers learn about spacecraft simulators, underwater spacewalk training, survival skills, swimming requirements, medical standards, interviews, education, and the different careers astronauts have followed before applying. Scientists, engineers, doctors, teachers, military pilots, geologists, and other professionals have all reached the astronaut corps by different routes. The book also looks at the realities of selection, including how competitive the process is and why there is no single guaranteed path. It explains the role of STEM education while also examining skills such as reading, physical fitness, handling mistakes, working with a team, speaking up when something seems wrong, and accepting responsibility. Each stage includes age-appropriate suggestions labeled MATTERS, HELPS, or NOT YET, followed by a practical timeline from childhood through middle school, high school, college, and early adulthood. The final chapters also consider careers in spaceflight for people who never become astronauts and how interests and goals can change along the way.