In this article we describe an approach to the design of learning objects (LOs) suitable to support learning in complex domains. We briefly discuss, from an educational point of view, the methodological choices underlying the design of LOs to be used as didactical materials in a distributed Web-based environment, presently under development, devoted to robotics education at the university level. We show how our pedagogical approach to knowledge acquisition and to the use of technological tools is realised by means of didactical units which can be implemented as LOs with various aims and correspondingly different structures. We also address the issue of supporting students' learning in ways that differ according to the requirements of each situation and illustrate how such support can be implemented by means of our pedagogically oriented LOs.