When it comes to mating, the male's role is often thought of as straightforward: to get sperm into the egg. However, male ejaculate contains a diverse mixture of seminal fluid proteins (SFPs) that are transferred along with sperm during mating. These proteins are essential for fertilization and have a great impact on the fitness of both males and females. They also have functions related to relative fertilization success in sperm competition, such functions often also mediate sexual conflict between sexes when they manipulate female behaviors and physiology. These incredible proteins are the main focus of my research. I aim to understand their evolution, functions, and role in non-genetic inheritance while using them as a tool to understand the fundamental principles of evolutionary biology.