Complex sentence: In 1899, he developed the Hershey process which is less sensitive to milk quality than traditional methods, and in 1900, he began manufacturing Hershey's Milk Chocolate Bars, also called Hershey's Bars or Hershey Bars.
Split into simpler sentences: In 1899, he developed the Hershey process, which is less sensitive to milk quality than traditional methods. In 1900, he began manufacturing Hershey's Milk Chocolate Bars, also called Hershey's Bars or Hershey Bars.