This new volume of Methods in Enzymology continues the legacy of this premier serial with quality chapters authored by leaders in the field. This is the first of two volumes on endosome signaling and includes chapters on such topics as measurement of entry into the endosomal compartment by multi-parametric image analysis, assessment of peptide internalization and endosomal signaling, and VEGF-A in endosomal signaling. Continues the legacy of this premier serial with quality chapters authored by leaders in the field Covers endosome signalingContains chapters on such topics as measurement of biological effects of endosomal proteolysis of internalized insulin and multi-vesicular endosome biogenesis.