Freier worked on her doctoral research with Edward Ney and Frank Oppenheimer, using high altitude balloons to study cosmic radiation.
In 1948, this research led to Freier becoming the first person to see tracks in nuclear emulsions, proving that nuclei of heavy elements were included in cosmic radiation.
[2][1] In 1988, Freier was recognized by the University of Minnesota with a distinguished teaching award for her outstanding contributions to the education of physics undergraduates.
She taught for eighteen years where she originated the application of student textbook learning to the laboratory settings.
At the University of Minnesota, she and her colleagues discovered the presence of heavy nuclei in cosmic radiation, which remains one of the key discoveries in astrophysics.