Hexapoda not only constitutes the largest taxon in the biological world; its representatives are also the best-studied invertebrates. This chapter will give an overview of general principles of hexapod development, mostly in reference to the detailed description of Drosophila melanogaster (see Chap. 1). The description will be divided along key developmental processes in early development, leading from oogenesis through early patterning and ending in segmentation. Later development is covered in Chap. 3.