Old and new: planets in the solar system and beyond

For thousands of years, our knowledge of planet has been confined within the solar system, which contains only a handful of known planets. Since 1990s, people have made enormous progress in the last 20 years. Thousands of extra-solar planets (exoplanets) have been detected, opening a new era for planetary research and extending our scope beyond the solar system.In this article, we briefly review the history of planetary research, introduce some key progress and hot topics in the field of exoplanet, and discuss its prospects in the near future.