Micropaleontology
Micropaleontology (also sometimes spelled as micropalaeontology) is the branch of paleontology that studies microfossils. Microfossils are fossils generally not larger than four millimeters, and commonly smaller than one millimeter. A microscope is used to study them. Every kingdom of organisms is represented in the microfossil record. Microfossils can provide important information about the ecology in the past.