The highly conserved influenza fusion domain (HAfp) is a strict requirement for fusion of the viral membrane with the host endosomal membrane. This step of the infection process is vital for influenza proliferation. HAfp is a highly conserved peptide with a unique amphipathic helical-hairpin structure. This thesis describes a broad investigation into the precise mechanism by which HAfp induces membrane fusion. Here we demonstrate that HAfp is capable of inducing negative membrane curvature correlated to its ability to promote fusion. This ability appears to be the result of a unique conical shape and a particular orientation of membrane insertion. Additional mutational studies reveal that such fusion induction is sensitive to even conservative mutations, which demonstrate varying effects on HAfp structure and dynamics. These mutational studies suggest that wildtype HAfp activity is highly nuanced, with refined features such as tertiary dynamics, overall geometry, binding kinetics and depth or angle of membrane insertion. This delicate balance relates well with the high degree of evolutionary conservation and may play an important role in the development of therapeutic measures.