Lamina emergent mechanisms (LEMs) are fabricated from planar materials (lamina) and have motion that emerges out of the fabrication plane. LEMs provide an opportunity to create compact, cost-effective devices that are capable of accomplishing sophisticated mechanical tasks. They offer the advantages of planar fabrication, a flat initial state (compactness), and monolithic composition (which provides the advantages associated with compliant mechanisms). These advantages come with the tradeoff of challenging design issues. LEM challenges include large, nonlinear deflections, singularities due to two possible motion configurations as they leave their planar state, and coupling of material properties and geometry in predicting mechanism behavior. This paper defines lamina emergent mechanisms, motivates their study, and proposes a fundamental framework on which to base future LEM design. This includes the fundamental components (created by influencing geometry, material properties, and boundary conditions) and basic mechanisms (including planar four-bars and six-bars, and spherical and spatial mechanisms).