<p>Spaceflight missions have advanced techniques over the last decades, with astronauts spending their time for more than 6 months aboard the International Space Station. Nevertheless, the living and working conditions in outer space remain highly challenging and demanding for astronauts. Space science has also been a frontier area in life science research, which targets studying the human physiology of living beings and their physiological changes under microgravity. This review highlights the impact of microgravity on the alteration of human, plant, microbial, and rodent physiology, emphasising the effects of microgravity on the physiology of these organisms in a space environment. Different countries have their own space agencies, and they have increased their space research over the past few decades in preparation for future space missions. The spaceflight radiation-induced carcinogenic effects have emerged as a health risk during deep spaceflight missions. In the recent era, a huge number of cell-line and animal model experimental studies have been conducted to explore the microgravity radiation, lower and higher doses of radiation, heavy ions, and low Earth orbital environments have identified evident carcinogenicity. Deep space flight mission leads to Spaceflight Associated Neuro-ocular Syndrome and associated other diseases such as glaucoma, alzheimer’s disease, cerebral edema, and cancer. In this review, we have summarized the objectives of space biology, the historical background of different space agencies, different types of space radiation associated with several diseases, multiscale biological experiments under microgravity, and biological specimen experiments under different space agencies.</p>