We performed 0- to 4-h timed lays and collected and fixed embryos according to Blythe and Wieschaus (2015). We then hand-sorted embryos using a Zeiss Discovery.V8 microscope under GFP excitation using an X-CITE 120Q stereo light source. We pooled 200 (NC 11–14) to 400 (NC < 11) embryos and performed ChIP as in Blythe and Wieschaus (2015) using 3 μL of rabbit anti-CLAMP antibody per sample.