Working life of today faces challenges. There is a fast pace in technical and organisational development and continual demands for increased performance. In order to manage the increasing complexity in work systems, there is a need to take a holistic view on operations. One such view is the systems concept of Humans, Technology and Organisation (HTO). The aim of this report is to describe the HTO concept, how it was developed, and how it can be used to develop work and work systems, understand humans at work, and understand contributing factors to organisational performance and individual well-being. The core of the HTO model is human work activity and how it is carried out within a work system consisting of humans, technology and the organisation. Focussing on human work activity generates knowledge about work conditions, needed competences and collective interaction, but also understanding about outcomes of the activities – the systems performance. H, the Humans in the work system, can be understood from different perspectives, for example as biological systems, information processing systems, individuals with unique personal traits and experiences, or as members of social groups. The H can thus in itself be regarded as a sub-system within HTO. In a similar way, T, Technology, includes several facets, such as tangible tools and machinery, intangible IT systems and software, and environmental characteristics that are technologically designed. The same applies for O, Organisation, consisting of both formal aspects (e.g. written work instructions and follow-up systems) and informal aspects (e.g. organisational culture and informal work practice). Applying HTO in practice generates several types of outcomes: 1) HTO to design products shows that it can be beneficial for productivity, quality and individual safety; 2) HTO to analyse and understand complex work may shed light on complex work in practice, the influences between the individual and the work system, and gaps between prescribed, standard work and how it is carried out in practice; 3) HTO to understand safety shows that it is achieved through systems thinking, thus technology needs to be designed to match human capabilities, and HTO barriers should be in place to prevent accidents; and 4) HTO to improve health and productivity may result in workplace redesign, increased individual well-being and business productivity. HTO has several uses, such as a theoretical framework, an analytical tool, and a method for a holistic view on human work, but also as a tool for visualisation and design.