Report produced in the project Enabling and Promoting Trust in Micro Service Environments (EPTMSE) with a web site at www.trust-eze.org. The report gives an overview of the concept of trust in domains such as psychology, sociology, philosophy, and computer science, and then describes the current domain of Micro Service Environments - open and unregulated electronic service environments - where users can create, use, and share electronic services, and where the need for decentralized trust mechanisms is high. Some design and implementation choices and solutions for trust mechanisms are suggested.