Placodes are transient, focal aggregations of ectoderm located in the developmental region of the future vertebrate head, and give rise to sensory organs. Early cranial sensory placodes are marked by expression of Six1, part of the Six family of transcription factors that regulate preplacodal ectoderm specification. The olfactory placode forms as two thickenings of non-neural region of embryonic ectoderm. In mice, the olfactory placode derives from an anterior portion of the neural tube, ~9-9.5 days into development and not long after the closure of the neural plate. Development of the olfactory placode requires the presence underlying neural crest-derived mesenchymal tissue. The specification of the olfactory placode tissue involves signaling of multiple gene networks, beginning with signals from bone morphogenetic proteins (BMP), retinoic acid (RA), and fibroblast growth factor (FGF), specifically FGF8. The resulting regulated downstream expression of transcription factors, such as Pax6, Dlx3, Sox2, and others, within the presumptive olfactory placode are crucial for sub-regionalization within the future olfactory epithelium and is responsible for the diversity of cells that compose the future epithelium.