The epidermis is every plant's interface with the environment. This dynamic tissue serves as a protective barrier against biotic or abiotic threats and controls the plant's exchange of gas, water and nutrients. Epidermal development is environmentally sensitive, allowing plants to adapt successive phytomers to serial stresses and opportunities throughout the growth cycle. During leaf development, cell patterning, cytological features and epicuticular wax deposition respond dynamically to environmental factors including CO2 concentrations (p[CO2]). Gas exchange is controlled by stomata, epidermal pores flanked by a pair of guard cells that regulate their aperture in response to light, humidity and p[CO2]. The number (stomatal density, SD) and proportion (stomatal index, SI) of stomata in the leaf epidermis directly affects the plant’s ability to control gas exchange and these metrics change in response to p[CO2]. In this study, changes in the leaf epidermis under elevated and ambient CO2 have been characterized across the plant life cycle and the genetic basis of these traits has been explored by quantitative trait locus (QTL) mapping of an Arabidopsis recombinant inbred (RI) population. In order to quantitatively characterize thousands of Arabidopsis leaf epidermis samples, a new method for high-throughput epidermal phenotyping was developed. Optical topometry (OT) is a fast, reliable method of surface metrology that allows for data-rich, non-destructive measurement of any surface at nanometer resolution. As a result of exploring this technology’s applicability to plant surfaces, I report a variety of epidermal features in over 30 accessions of Arabidopsis plus other species, including herbarium and fossilized samples. OT was used to track morphological changes on the plant epidermis and can also be used to measure difficult phenotypes such as cuticular wax levels and stomatal depth. The high-throughput, high-resolution capabilities of OT were used to conduct a QTL mapping study to identify loci involved in epidermal patterning and stomatal characteristics under varying p[CO2]. Using the Bay x Sha RI population, 10 gene loci were identified that putatively contribute to eight leaf epidermal traits. The information provided by the QTL analyses creates a strong foundation for a genome-wide association study to better understand the genetic influence of these ten loci. The final chapter of this thesis describes how stomatal development, specifically SI, is affected by p[CO2] across leaf tissue at different stages in the plant life cycle. The data suggest that p[CO2] regulation may be controlling SI via satellite stomata formation and that SI can be affected by the environment conditions experienced by older tissue, including a seed's the maternal environment as well as that under which it germinates. Together these results expand our current understanding of epidermal patterning under varying p[CO2] and the role of p[CO2] in stomatal development.