Small-molecule fluorescent probes have become powerful tools for using light to advance the study of cell biology, discover new drugs, detect environmental contaminants, and further the detection of cancer. These applications correlate with the expansion of the fluorescent probe research community - small in the late 20th century, now a collection of more than a hundred research groups world-wide. This expansion required the entry of adventurous scientists from many other fields. This tutorial review introduces some important concepts related to fluorescent probe development. It is hoped that it will facilitate further expansion of the field by demystifying it.