Following a long history of quantitative genetics in crop plants, it now becomes feasible to use naturally-occuring variation contained in Arabidopsis thaliana accessions (lines isolated from natural populations) as the source of quantitative genomics approaches, designed to map QTLs and resolve them at the gene level. Apart from being able to exploit in multiple genetic backgrounds allelic variation that cannot be easily generated by conventional mutagenesis, the (relatively few) success of the QTL studies has often been because of the use of quantitative phenotyping, as opposed to the qualitative gauges used in typical mutant screens. Among the various genetic mechanisms responsible for natural variation that have just started to be revealed, cis-acting regulation is potentially of large impact, despite remaining more difficult to recognize and confirm. The objective of this project is to apply genome-wide quantitative molecular genetics to both, a very integrative and classical quantitative trait (growth in interaction with the environment) and a molecular trait a priori more directly linked to the source of variation (gene expression under cis-regulation). We propose to use a combination of our unique high-troughput phenotyping robot, fine-mapping, complementation approaches and association genetics to pinpoint a significant number of QTLs and eQTLs to the gene level and identify causative polymorphisms and the molecular variation controlling natural diversity. Working at an unprecedented scale should finally allow to resolve enough quantitative loci and pay a significant contribution to drawing a general picture as to how and where in the pathways adaptation is shaping natural variation and improve our understanding of the transcriptional cis-regulatory code.