Considering the increasing demand for microlearning in informal learning spaces, the main purpose of this research is to examine the design of microlearning perceived by adult learners and experts in Korea. The research questions include: (1) what modality and content length do adult learners perceive to be relevant for microlearning? (2) what content areas do adult learners perceive to be relevant for microlearning? and (3) what are the expected impacts and future directions of microlearning perceived by the experts? The participants include 11 e-learning experts and 326 adult learners working in the fields of science and technology. Data were collected from the learner survey, focus group interview, and expert survey. Overall, this study found that adult learners tend to have some conflicting opinions about the content areas perceived to be relevant for e-learning and microlearning. The design of content that takes the modality of video consumed within 3-5 minutes was considered to be the most relevant for microlearning. Experts perceived that microlearning is an efficient and effective direction for adult learners to enhance professional knowledge and to broaden informal learning opportunities. However, the experts were less positive about the potential of microlearning for increasing convergence research and learning transfer. There was a considerable gap between desirability and feasibility in the directions toward integrating microlearning with advanced technologies. Based on the key findings, we discuss some implications concerning the design of microlearning for adult learners' informal learning.