Optical molecular probes can be used as targeted beacons to visualize a specific site in a cell or living subject. Optical probes in this thesis are colorimetric or fluorescent and usually they have a targeting group attached to the reporter group. Chapter 1 of this thesis provides an overview of optical molecular probes and the dyes used for encapsulation. Chapter 2 describes the synthesis of an extended squaraine dye that exhibits a red shift in fluorescence, with a narrow and distinct signal. Chapter 3 describes the application of squaraine dyes in pre-assembly as fluorescent molecular probes for biological targeting. Chapter 4 describes the application of croconaine dyes as photothermal agents for use in targeted cell heating. Finally, Chapter 5 explores the visual optimization of colorimetric assays with resorufin probes.