Learners are increasingly using digital and networked technologies to access instruction. This revolution in how education is delivered carries important affordances and serious limitations that must be considered when designing online instruction. Online instruction allows learners greater flexibility and control over their learning, can include engaging and helpful multimedia representations of knowledge, can provide social interactions, and can be scaled to reach broader audiences of students. However, significant costs come with these advantages. Online environments typically demand greater self-regulation skills, impose larger cognitive loads, challenge students’ motivation, and limit social learning. Possibilities for overcoming these challenges, including various forms of scaffolding, are discussed.