Ice crystals are the most ubiquitous material found in the cryosphere environment of the Earth, in the planetary system, and also in our daily lives. In recent years, ice crystals have increased in importance as one of the key materials for finding solutions to settle various environmental concerns at a global scale. Furthermore, ice crystals are unique materials which are potentially extremely useful in various applications, for example, within the food sciences, medical sciences, and other fields. In dealing with these interesting subjects, research on ice crystals has been more actively pursued in recent years. The Special Issue "Ice Crystals" presents a wide varieties of topics related to ice crystals. It can be considered as a status report reviewing the recent research on ice crystals and serves to provide readers with information on the latest developments concerning ice crystals.