Want to come visit, build and explore -- after-school or on the weekend? We have several (free!) drop-in programs for you to visit. During these programs, we open our doors to the community, where scientists of all ages can explore our space at no cost. Every Tuesday after-school at Excelsior Site: Every Tuesday of the school year, 3pm - 5pm. First Saturday at Bayview Site: Every 1st Saturday of each month of the school year, 10am to 3pm. Second Saturday at Mission Site: Every 2nd Saturday of each month of the school year, 10am to 3pm. Third Saturday at Excelsior Site: Every 3rd Saturday of each month of the school year, 10am to 3pm.