Hybridization chain reaction (HCR) using probes for Snai2, Sox9, Sox10, and Pax7 in (A-L1) quail and (M–X) chick embryos. (A, G, A1, G1, M, and S) are Snai2 (red). (B, H, D, J, D1, J1, P, V) are Sox9 (green). (E, K, Q, W) are Sox10 (cyan). (N, T) are Pax7 (magenta). (C, C1, F, F1, I, I1, L, L1, O, U, R, and X) show overlays of two genes. Arrows indicate positive signal, while asterisks indicate no signal. Scale bars as as marked in rows.