The 2021 NEURON Online Course will start on Thursday, June 3, 2021, and will meet Tuesdays and Thursdays thereafter until Tuesday, August 3. This course maps the first half of the NEURON Summer Course into a series of interactive online workshops about building and working with models of single neurons. It is suitable for individuals at all levels of expertise. Although it focuses on modeling individual cells, the topics it covers are the foundation for modeling networks with NEURON. Space is limited, and applications will be considered in the order received. The registration deadline is Monday, May 31, 2021. No applications will be accepted after that date. For more information and the on-line registration form, see https://neuron.yale.edu/neuron/static/courses/web2021/june.html --Ted