nucleus, check

核 is composed of 木 (wood) and 亥 (12th earthly branch). 木 represents plants, while 亥 depicts the skeleton of an animal’s body. The skeleton is wrapped in flesh and skin and carries the sense of a center, much like the seed inside a plant’s fruit. Therefore, 核 is used to mean the central part of a thing. In addition, to thoroughly understand something, one must also examine its central part clearly. Therefore, 核 also means to examine or to investigate.