A flatbread is a simple bread made with flour, water, and salt and then thoroughly rolled into flattened dough. Many flatbreads are unleavened — made without yeast or sourdough culture — although some flatbread is made with yeast, such as flatbread made with whole wheat flour. There are many other optional ingredients that flatbreads may contain, such as curry powder, diced jalapeños, chili powder or black pepper. Olive oil or sesame oil may be added as well. Flatbreads can range from one millimeter to a few centimeters thick. Flatbread was already known in Ancient Egypt and Sumer.