Title: A Gradient-Based Approach to Neural Networks Structure Learning. Abstract: Designing the architecture of deep neural networks (DNNs) requires human expertise and is a cumbersome task. One approach to automatize this task has been considering DNN architecture parameters such as the number of layers, the number of neurons per layer, or the activation function of each layer as  hyper-parameters, and using an external method for optimizing it. Here we propose a novel neural network model, called Farfalle Neural Network, in which important architecture features such as the number of neurons in each layer and the wiring among the neurons are automatically learned during the training process. We show that the proposed model can replace a stack of dense layers, which is used as a part of many DNN architectures. It can achieve higher accuracy using significantly fewer parameters.  