Emoticons are schematic facial expressions or little pictographs, which are added to electronic messages. Following a complete review of the literature on Computer-Mediated Communication and emoticons, this dissertation analyses the history of emoticons, their typologies and discusses their current spread. The empirical part of this doctoral work is based on an exploratory survey and the analysis of a corpus. The survey was answered by a convenience sample of 226 people. It considered some understudied aspects in research on emoticons, as the settings in which emoticons are mostly used, the most recurring contexts in which they appear and the possible reasons for the current success of emoji. The survey also investigated the agreement of respondents regarding the meaning they would attribute to a set of 19 graphical emoticons, in order to assess the interpretation of these pictographs and the emergence of a conventional meanings. The corpus is composed by a sample of WhatsApp chats. This is a popular instant messaging application for smartphones, which is really popular in Spain. The methodology for the corpus analysis integrates two different approaches: on one hand, Computer-Mediated Discourse Analysis (Herring, 2004), consisting in applying linguistic methods to online corpora, and social semiotics (Kress & Van Leeuwen, 2006), a recent perspective that analyses human communication considering non-linguistic materials, too (Adami, 2016; Jewitt, 2009). Results confirm the popularity of emoji, the preference for the traditional yellow faces and a clear preference for the use of emoticons in informal registers and positive contexts. From an intersemiotic point of view, the relationship between text and images is widely metonymic. The functions of emoticons may be varied (politeness, enhancement of the message, signaling informality, replacing words, managing turn-taking, etc.). Their use seldom provoke misunderstandings. Moreover, the dissertation considered social and cultural aspects related to the use and spread of emoticons, WhatApp and the current digital culture.