Photochemical uncaging of bio-active molecules was introduced in 1977, but since then, there has been no substantial improvement in the properties of generic caging chromophores. We have developed a new chromophore, nitrodibenzofuran (NDBF) for ultra-efficient uncaging of second messengers inside cells. Photolysis of a NDBF derivative of EGTA (caged calcium) is about 16 -160 times more efficient than photolysis of the most widely used caged compounds (the quantum yield of photolysis is 0.7 and the extinction coefficient is 18,400 M-1 cm-1). Ultraviolet (UV)-laser photolysis of NDBF-EGTA:Ca2+ rapidly released Ca2+ (rate of 20,000 s-1) and initiated contraction of skinned guinea pig cardiac muscle. NDBF-EGTA has a two-photon cross-section of ~0.6 GM and two-photon photolysis induced localized Ca2+-induced Ca2+ release from the sarcoplasmic recticulum of intact cardiac myocytes. Thus, the NDBF chromophore has great promise as a generic and photochemically efficient protecting group for both one- and two-photon uncaging in living cells. © 2006 Nature Publishing Group.