The functioning of the immune system depends upon exquisitely choreographed interactions between its cellular constituents. Two-photon microscopy now enables us to visualize cell motility and cell-cell interactions deep within intact tissues and organs, both in explanted preparations and in vivo. Real-time immunoimaging techniques have illuminated the roles of random and chemokine-driven motility for cellular search strategies, the complex dynamics of cellular interactions, and the micro-anatomical localization and control of lymphocyte trafficking. Recently, advances have been made in these areas of research, as exemplified by studies investigating T cell-dendritic cell interactions, T cell-B cell interactions, and the regulation of lymphocyte egress from the lymph node.