© 2016 Elsevier Inc. All rights reserved. Many cellular functions, including proliferation, migration, and gene expression, are regulated by multiple processes acting across multiple spatial and time scales. While mathematical models of the constituent processes can provide insight into aspects of a particular cell function, the models must be combined to provide a more complete understanding of the system. Vertical integration is the merging of models formulated at different spatial and/or temporal scales to produce multiscale models. This article provides an introduction to vertical integration. We explain how multiscale models may be assembled, the insight they may generate, and the challenges associated with their development and validation.