Three stages of the merger illustrated by X-ray and optical images of three massive clusters. From top to bottom: Before the pericenter passage (MACS J0416), shortly after pericenter passage (CL0238), and slightly later (Bullet). The left panels show Chandra X-ray images. The panels in the middle present the residuals after the best-fitting symmetric model of a cluster+background was subtracted from the X-ray image and after dividing by the model (i.e., ${\displaystyle \frac{\mathrm{image}-\mathrm{model}}{\mathrm{model}}}$). The right panels show the optical DESI r-band images.