Complex sentence: Albert Robert Valentien (1862--1925) was an American painter and ceramic artist, best known for his work as the chief decorator at Rookwood Pottery and for his watercolor paintings of botanical subjects.
Split into simpler sentences: Albert Robert Valentien (1862--1925) was an American painter, botanical artist, and ceramic artist. He is best known for his work as the chief ceramics decorator at Rookwood Pottery, and for his watercolor paintings of botanical subjects.