Emily Riehl is a mathematician and category theorist, her talk at Lambda World investigates computational effects using category theory. She begins by establishing a mathematical point of view and then outlines what a category is. Generally, we may think of a category as something which certain things may be grouped in because of their similar properties and a category may be separated from another category because of their differences. Emily defines a category as a two-sorted structure that encodes the algebra of composition. In the latter half of her talk, Emily discusses monads vs. Lawvere theories.