Whether we are aware of it or not, in our daily life we are surrounded by networks through which we interact and whose structure is modified by our actions or decisions. Our friendships and relationships are part of a bigger network in which people influence each others' opinions, the roads we travel every day are part of a wider traffic network, the web-pages we consult form part of the World Wide Web (WWW), our social media profiles are immersed in a broader structure where contents are shared. Moreover, by meeting a new person, by adding a new hyperlink in our website, by commenting or liking a post on someone else Facebook page, we actively contribute to form and modify the shape of the network.