Activation and inactivation of proteins using photoactivation of caged peptides or proteins offer insights into cellular dynamics not achievable using genetic means. The ability to selectively alter the activity of a specific protein at a defined time and location inside a cell allows the correlation of changes in protein activity and cellular behavior. A caged compound, peptide, or protein is prepared by covalently linking it to a photolabile, protecting group. - [Read Introduction of Caged Peptide/Protein into Cells Using Microinjection Protocol]