CNNs perform well at classifying images. However, if the images have rotation, tilt, or any other different orientation, then CNNs show relatively very poor performance. Even the pooling operation in CNNs cannot much help against the positional invariance.
This issue in CNNs has led us to the recent advancement of CapsNet through the paper titled Dynamic Routing Between Capsules (see more at https://arxiv.org/abs/1710.09829) by Geoffrey Hinton et al.
Unlike a regular DNN, where we keep on adding layers, in CapsNets, the idea is to add more layers inside a single layer. This way, a CapsNet is a nested set of neural layers. We'll discuss more in Chapter 11, Discussion, Current Trends, and Outlook.