Professor Sallie “Penny” Chisholm delivered the 43rd James R. Killian Lecture to a full house on March 10, 2015. Her talk, entitled “Tiny Cell, Global Impact: A journey of discovery with a microbe from the sea”, discussed her unprecedented work on photosynthetic organisms in the ocean – specifically Prochlorococcus. In 1988, Chisholm led a team that discovered this microorganism and determined it to be one of this planet’s most abundant photosynthetic creatures and major regulator of the oxygen in Earth’s atmosphere today. “The complexity of this system is incredibly humbling,” Chisholm said. Read the MIT News article or watch the lecture.