10% of global child mortality is due to diarrheal disease. We now understand the protozoan parasite Cryptosporidium to be a leading cause of this burden with a particular grave impact on malnourished infants and toddlers. Boris Striepen’s laboratory has pioneered molecular genetics for this previously intractable pathogen. The lab uses genetics and genomics to understand fundamental parasite cell and molecular biology. How does the parasite’s complex sexual lifecycle unfold, and how do parasite, host and commensals interact to shape susceptibility, disease and protection? Some of these insights and tools have enabled translation and the search for effective anti-parasitic treatment and prevention. Boris has also been engaged in education, he taught undergraduate and graduate classes, directed an NIH training program, and served as faculty and director of the Biology of Parasitism summer research course at the Marine Biological Laboratories in Woods Hole.