This is clipart converted and broken apart that has been released into the public domain because the document says so, and its from NASA, a USA government agency. The publication is called "The Brain in Space:" http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/The.Brain.in.Space.html
藏寶圖
astronomy、brain、converted、government、nasa、science、space、usa、Useful icons for powerpoint for work
天文學、腦、轉換、政府、上、科學、空間、使用、Powerpoint的有用的圖標為工作
資料來源：openclipart ( https://openclipart.org/ )