Complex sentence: Jeffrey Mogil studied the facial expressions of mice during increments of increasing pain; were five recognizable facial expressions; orbital tightening, nose and cheek bulge, and changes in ear and whisker carriage.
Split into simpler sentences: Jeffrey Mogil studied the facial expressions of mice during increments of increasing pain. What they found were five recognizable facial expressions; orbital tightening, nose and cheek bulge, and changes in ear and whisker carriage.