Correlative light and electron microscopic exploration of endocytic organelles

Explorations of endocytic pathways teach us about subcellular routes travelled by pathogenic agents, such as viruses and toxins, and used for targeting of drugs into the interior of cells. In this compendium we show a correlative microscopic approach that uses the photooxidation capacity of fluorescent dyes to oxidize the substrate diaminobenzidine which after osmification is visible in the electron microscope. The method combines the advantages of both light and electron microscopy: light microscopically, it is possible to study cells in vivo, and to see the samples in a survey, which allows recognition of diversities within tissues and cell cultures; the fine structure then can be clarified in the electron microscope.