The heart of many active and cooperative learning strategies lies in successfully engaging small groups of students in the task of solving problems (or working on other projects, such as experiments or other research) that are challenging enough to require the participation of all the students in the group. Herein also lie the difficulties associated with the implementation of these methods. Namely, great care must be taken in the design of the problems or projects so that they are neither too easy nor too difficult. Perhaps even more crucial is the task of taking adequate steps to ensure that groups function so that all the students benefit from the interaction. Moreover, since group work may also serve to provide a coherent context for the students to integrate material from different components of the course (labs, lecture, homework, exams, etc.), assessment of the efficacy of group work may play a pivotal role in understanding the extent to which many of the overall learning goals for a course are being achieved.