"' Using live cell FRET biosensors, cells induced with different concentrations of EGF illicit activity bursts of different frequency, where higher levels of EGF resulted in more frequent bursts of ERK activity. Furthermore, the dynamics of ERK activation in response to mitogens were found to be relevant for unique downstream responses including timing of S-phase entry in MCF10A cells. Various types of growth factors can also lead to unique ERK dynamics in other cell types effecting cell fate, suggesting the temporal dynamics of ERK activation is a general means of encoding unique gene expression programs by cells.