Spike-ins: At what stage of the ChIP experiment do you introduce the spike-ins?

There are a few different stages when you can add the spike-ins. The most important thing is to make sure they are combined prior to the pull-down step. This includes combining cells together, combining spheroplasts together, combining nuclei together, or combining fragmented DNA together. by Tovah Markowitz, Paul Schaughency, Vishal Koparde.