LipoFluor-ER2™ is a cell-permeant stain for the endoplasmic reticulum with unique spectral properties, which makes it particularly useful for antibody double- and triple-labelling experiments. LipoFluor-ER2™ is highly compatible with green, red and far-red fluorophore-labelled antibodies and has been successfully used to image the endoplasmic reticulum in human and other mammalian cell lines. It passively diffuses across the plasma membrane into the cell, stains at low concentrations and has minimal cytotoxic effects. This tracing reagent can be used on live and fixed samples, is compatible with other dyes, shows excellent resistance to photobleaching and demonstrates low cytotoxicity.