There is an urgent need to understand how organisms will adapt to today's rapidly changing environment. Adaptive evolution occurs when genes affect traits under natural selection, but most previous studies have been unable to identify the specific ecological factors involved. By combining molecular, evolutionary and ecological information, we can help to fill this gap in knowledge and answer fundamental biological questions about how natural selection acts on genetic variation in the wild. The deer mouse is the most common mammal in North America and exhibits substantial variation in its coat colour. In the Sand Hills of Nebraska, it has been shown that coat colour often matches substrate colour (light tan with light brown sand or dark grey with dark soil), which camouflages the mice and improves their chances of survival against predation by birds. In order to take advantage of this outstanding opportunity to study adaptation, large experimental enclosures were established on both substrates and populated with mice of both colours. DNA from each mouse is sequenced so that we can see how genes change over time. This innovative experiment allows us to directly observe genes being influenced by known ecological factors in natural populations. Initial results show significant changes across the genome and not just in the pigmentation genes. My Ph.D. at McGill University will focus on these genes and their consequences for survival and reproduction. The grand scale of the field enclosures and the extensive depth of genetic sampling in this ambitious experiment are very rare and will lead to valuable insights in this growing field of “experimental genomics”. Environmental change often results in higher extinction rates and poses a significant threat to Canadian and global biodiversity. Understanding the genetics of adaptation will allow us to better predict how natural populations will respond to human-induced changes in the environment and help prevent extinctions.