This article is about the beginnings of tissue culture-the culture of living, reproducing cells of complex organisms outside the body. It argues that Ross Harrison's experiments in nerve culture between 1907 and 1910 should be viewed as part of a larger shift in early twentieth-century laboratory practice from in vivo to in vitro experimentation. Via a focus on the temporality of experiment-contrasting the live object of Harrison's investigation with the static object of histological representations-this article details the production of a (...) new and surprising form of life, cellular life in vitro. Tissue culture, developed from Harrison's experiments, was greeted with great surprise and disbelief, despite Harrison's protestations that he had merely juxtaposed extant techniques. An analysis of these initial reactions to tissue culture illuminates the extent to which cells living visibly outside of the body in glass broke with in vivo practices and assumptions of the hiddenness and interiority of certain processes of growth and change. (shrink)