Long-term observation of cell behavior at the single cell level is a crucial prerequisite for understanding molecular cell fate control. This is of particular importance when analyzing highly dynamic and heterogeneous developmental and stem cell systems. The required observations are possible by time-lapse microscopy, but reliable identification of specific cell types and maturation stages usually requires detection of molecular marker expression. However, only few of the necessary cell or animal lines expressing genetically encoded fluorescent markers exist, and the generation of novel reporter lines is laborious and slow. Here, we describe long-term antibody staining in living cell cultures as an easy, robust, flexible and fast way of continuous real-time marker detection on living cells. This approach greatly simplifies the live identification of specific cell types in heterogeneous and dynamic culture systems.