Spatial partitioning in ecological communities has predominantly been described in two dimensions, yet habitat is complex and 3D. Complex space use mediates community structure and interaction strength by expanding spatial, temporal, and dietary dimensions. Vertical stratification of resources provides opportunities for novel specializations, creating a 3D niche. Competition and predation are mediated by 3D space use, as individuals use the vertical axis to access prey, flee predators, or avoid competitors. The 3D niche is important for long-term conservation strategies as species must navigate tradeoffs in habitat use between strata-specific threats and suboptimal habitat patches. Ultimately, elucidating the 3D niche has implications for protected area management and corridor design that directly influence species persistence and ecosystem function in a rapidly changing world. A ‘3D niche’ occurs where the environment or habitat is stratified vertically, adding additional complexity for community structure, creating opportunities for species to specialize in those spaces.Structural complexity is a better predictor of biodiversity in forest ecosystems than simple measures of canopy cover. Further, structural complexity can influence broader-scale community assemblages by increasing local species richness.Vertical forest habitat can provide valuable space to access prey, avoid pressure from dominant competitor species, and move up to favorable temperature refugia. A multitude of potential future research avenues exist within the 3D niche framework, from methodology to restoration to protected area design.