Microarrays employing a fluorescent ligand including a material having a binding affinity in the range of about 0.01 to about 25 nM, or about 0.1 to about 10 nM; a specificity to its cognate receptor in the range of about 50 to about 99%, or about 65 to about 99%; a cross-activity to other receptors of 0 to about 20%, or 0 to about 10%; a net charge per ligand of about −3 to about +5, or more preferably, about −2 to about +2 or most preferably for small compound ligands about −1 to about +2. The ligand may also have a hydrophobicity in the range of about 3 to about 55 minutes eluting time (as measured under specified eluting conditions). In some embodiments, the ligand includes fluorescently labeled motilin 1-16 labeled with Bodipy-TMR, rhodamine or Cy5-. Other embodiments include fluorescently labeled Cy5-naltrexone, Cy5-neurotensin 2-13, N-terminal labeled neurotensin 2-13 or lys-labeled labeled neurotensin 2-13.