Dramatic changes in gene expression take place during wing differentiation. A compressed heat map shows significant global gene expression changes for 8338 genes in the wing between late L3 and 36 h APF (proliferating L3 wing tissue was used as the reference sample). Each row corresponds to a single gene and each column represents an individual time point. Expression values (log2) are color coded according to the legend at the top. Using k-means clustering (see Materials and Methods), genes were grouped into 30 clusters based on expression profile similarities. Expression plots are shown for selected k-means clusters and approximately aligned to corresponding regions of the heat map. Plots of all 30 k-means clusters are shown in Additional file3. For each cluster, the normalized log2 expression level of each gene (grey lines) is plotted as a function of time (x-axis). The magenta line represents the average expression of all genes within a cluster. Examples of genes and enriched gene ontology terms for the selected clusters are listed at right.