Â­Mesoamericans began writing during the mid-Pre-classic period. The Mayans were the first to keep any sort of historical record, and the beginnings of the calendar were born. The Mayans used stelae, or stone monuments, to carve their civil events, calendars and astronomy knowledge. They also inscribed their religious beliefs and mythology on pottery.
The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is commonly the most prominent organelle in the cell. The nucleus is surrounded by a structure called the nuclear envelope.
Those that are eukaryotes have cells that contain a nucleus. The nucleus is an organelle that contains the genetic information for that organism. In an animal cell, the nucleus is located in the central region of the cell. In a plant cell, the nucleus is located more on the periphery due to the large water-filled vacuole in the center of the cell.