Onigiri , also known as omusubi or nigirimeshi (握り飯), is a Japanese rice ball made from white rice. It is usually formed into triangular or cylindrical shapes, and wrapped in nori (seaweed). While modern onigiri can be filled with a wide variety of ingredients, including both savory and sweet fillings, traditional fillings are often salty or sour, such as salted salmon, umeboshi, katsuobushi, kombu, tarako or mentaiko, or takanazuke. Because it is easily portable and eaten by hand, onigiri has been used as portable food or bento from ancient times to the present day.