Professor Cline's major focus is on Astroparticle Physics - connecting the world of elementary particles with Cosmology and Astrophysics. One topic of interest is the possible existence of a mass for the cosmologically interesting mu or tau neutrinos and methods to detect this mass using terrestrial solar or supernova neutrino sources. He participates in a collaboration to develop a supernova burst observatory in New Mexico for this purpose. Another study is the solar neutrino puzzle and nucleon decay using the ICARUS detector at the Gran Sasso Laboratory in Italy. Dr. Cline recently started to study the unique detection of Primordial Black Holes. These objects would have been born in the very early universe and would provide the ultimate merger of particle physics and strong gravity. These activities are supported by the DOE. Dr. Cline is also studying various types of gamma-ray telescopes for future gamma-ray Astronomy programs.