DNA can be self-assembled into molecularly precise, well-deﬁned, synthetic assemblies on the nanoscale, commonly referred to as designer DNA nanodevices. My lab creates synthetic, chemically responsive, DNA-based ﬂuorescent probes. In 2009 my lab discovered that these designer nanodevices could function as quantitative ﬂuorescent reporters to spatiotemporally image second messengers in living systems. Until this innovation, it was not at all obvious whether such DNA nanodevices could function inside a living cell without being interfered with, or interfering with, the cells own networks of DNA control. In my talk I will discuss how we get our DNA nanodevices to interface with the cellular world in programmable and targeted ways, function as ﬂuorescent reporters and quantitate an analyte within speciﬁc organelles of targeted cells within a living multicellular organism.[4-6] I will describe our most recent work - a ﬂuorescent reporter for chloride in live cells,[6,7] the ﬁrst in vivo measure of chloride (unpublished) and how by quantifying organelle function DNA nanodevices can report on disease severity (unpublished).
 Angew. Chem. Int. Ed. 2011, 50, 3124-3156;  Ann. Rev. Biochem. 2016 in press;  Nature Nanotechnol.2009, 4, 325-330;
 Nature Nanotechnol. 2013, 8, 459-467;  Nature Commun. 2011, 2, 339;  Nature Nanotechnol. 2015, 10, 741-747; Nature Nanotechnol. 2015, 10, 645-651;  Chem. Sci. 2016, 7, 1946-1953.