The volume of non tangible investments undertaken by firms has grown extraordinarily in the second half of the twentieth century, and it keeps growing in the present century. For that reason, issues related with the economic nature of intangibles, its identification and measurement are among the main interests of managers, investors, financial analysts and the rest of constituencies with interests in organizations. In this editorial, we review the evolution of the research about intellectual capital, defined as the set of intangibles of the firm, from its beginnings at the start of the nineties, to the most recent contributions, where it is defined as
the difference between intangible assets and intangible liabilities.