On April 12, 1961, Yuri Gagarin proclaimed the arrival of a new space age. The rapid advances in the different space sciences and technologies began after the first human spaceflight. Then fundamentally new sciences and technologies appeared. At present, space science covers a broad range of disciplines. The following outline is provided as an overview and topical guide to space sciences: Astronomy and Space Astronomy, Cosmology, Astrophysics, Space Physics, Solar-Terrestrial Physics, Aeronomy, Solar physics, Heliospheric Physics, Cosmic Ray Physics, Space Weather and Space Climate (Earth-Space Climatology), Space Dosimetry, Space Chemistry or Cosmochemistry, Remote Sensing of the Earth and Planets, Planetary Science, Planetary Geology, Astrogeology or Exogeology, Exoplanetology or Exoplanetary Science (Science for Extrasolar Planetary Systems), Intelligent Life in the Universe, Astronautics (or Cosmonautics), Orbital mechanics or Astrodynamics, Space life sciences: Bioastronautics, Space Medicine, Space Neuroscience, Space Biology, Radiation Biology, Biotechnology, Space Botany or Astrobotany, Microgravity Environment Research; Archaeoastronomy, Space Anthropology, Xeno-anthropology (Exo-anthropology), Space Law, Space Technology, Space Navigation, Space Communications, Space Architecture, Space Logistics, Space Robotics, Space Robotic Colonies, Space Colonization (also called Space Settlement or Extraterrestrial Colonization), Planetary Habitability, Space Manufacturing, Space Materials Science, Satellite Industry, Space Business, Space Tourism, Space Hardware, Space Industry, and Space Ecology. With the help of these advanced space sciences humankind began confidently the exploration of space. But these studies led also to numerous new technologies and applications to improve people's lives. Finally, we mention again Yuri Gagarin and his cosmic heritage. He left behind an inspirational legacy, which even today still continues to motivate millions of people worldwide.