The Sui and Tang dynasties reunified China and established centralized governments. The Tang expanded Chinese influence abroad through conquest and trade. Culturally, this was a high point of Chinese poetry, art, and invention, including gunpowder, the compass, printing, and paper money. The Song dynasty strengthened China's government and civil service. Culturally, the Song era saw advances in painting, porcelain, architecture, and moveable type printing. Both eras were times of economic growth, urbanization, and cultural exchange, though women's status declined.