Only about 600 people have traveled to space, mostly middle-aged men on short missions. Today, private and multinational spaceflight is ushering in a new era with longer missions and more diverse travelers, including women and people of various ethnicities and health statuses. As space exploration expands, researchers aim to understand the health effects of spaceflight to keep astronauts healthy. In 2019, the NASA Twins Study provided groundbreaking insights into the impact of a year in space on the human body. I am a radiation cancer biologist at Colorado State University.