Selenium is the element being discovered by Sweden chemist Jons Jacob Berzelius in 1818. It is named after Selene, the goddess of full moon in Greek mythology. Selenium-containing compounds/materials have been widely employed for their unique bio- and chemical activities [
1–
11]. It is an essential trace element for human beings and animals. It is one of the eight scattered elements in the world. In China, more than 70% of regions are selenium deficient [
12]. Selenium deficiency may lead to various diseases, including the brain diseases. It will cause irreversible damage to human brain tissue. The human body can maintain the selenium content in advanced central brain tissue by mobilizing the selenium content in other tissues of the body [
13]. Interestingly, when selenium is supplemented to selenium deficient animals, most of the element preferentially enters the brain tissues [
14]. These phenomena indicate the significances of selenium for maintaining the brain functions of both human beings and animals. With the discovery of a series of selenoproteins and selenium-containing materials, the biological function of selenium and the effect and mechanism of selenium deficiency on the body have been studied more and more deeply. It is found that selenium can participate in many functions of the central nervous system, such as motor ability, physical coordination, brain memory and cognition, showing that the element can play an important role in brain signal transduction pathway (
Fig. 1) [
15]. Selenoproteins in the body are essential for maintaining normal brain function. The reduction of selenoprotein function will lead to brain cognitive dysfunction and nervous system coordination disorder. Appropriate selenium supplementation can alleviate the clinical symptoms of some neurodegenerative diseases [
16]. Moreover, selenium has also been proved to be effective in antagonizing the toxicity of various heavy metals and the damage of environmental toxins to the nervous system [
17,
18]. Recently, the applications of selenium nanomaterials in nervous system afford additional opportunities for research in the field. Investigations on the relationship of selenium with health is booming. However, it should be noticed that excessive selenium intake may be harmful for health. The Institute of Medicine of the National Academy of Sciences stipulates that the maximum intake of selenium per adult per day should not exceed 400 µg [
19]. This paper aims to review the recent progresses and give a perspective.