Chemical Tools for Imaging, Manipulating, and Tracking Biological Systems: Diverse Chemical, Optical and Bioorthogonal Methods, Volume 641 in the Methods in Enzymology series, continues the legacy of this premier serial with quality chapters authored by leaders in the field. Chapters in this new release include caged cyclopropanes with improved tetrazine ligation kinetics, an analysis of metabolically labeled inositol phosphate messengers by NMR, cell-permeant caged inositol pyrophosphates for probing β-cells, imaging phospholipase D activity with clickable alcohols via transphosphatidylation, fluorescent biorthogonal labeling of class B GPCRs in live cells, near-infrared photoactivatable nitric oxide donors with integrated photoacoustic monitoring, and much more.