Crosstalk in PCB and packaging interconnects is arguably one of the most complicated phenomena that may cause signal degradation. Crosstalk effects can be treated statistically as a deterministic jitter with a bounded distribution, but the distribution is usually not known. A direct analysis of a worst-case crosstalk scenario may lead to a system overdesign. Neglecting it in design may cause a system failure that is difficult to find and fix later in a design process. Distortions caused by crosstalk cannot be corrected by signal conditioning techniques at a receiver side. It is very important to understand the sources of crosstalk, how to quantify it and how to mitigate it efficiently, as Yuriy Shlepnev demonstrates in this installation of the "How Interconnects Work" series.