Optical Project Tomography (OPT) (Sharpe et al 2002 DOI: 10.1126/science.1068206) was developed by James Sharpe while studying limb development, initially as a member of the Davidson Group at the MRC Human Genetics Unit and in collaboration with Ulf Ahlgren in the Group of Bob Hill and with the Mouse Atlas Project in the same Unit. The technique was aimed to capture of full 3D images of tissue structures in the size range of developing limbs and mid-gestation mouse embryos. This afforded the opportunity for the Mouse Atlas Group to generate true 3D models of mouse embryos as a preliminary to more detailed reconstruction of the same specimens from histological sections (the principal models of the eMouseAtlas, post E9). OPT also provided the opportunity to capture gene expression patterns in mouse embryos in full 3D. The bulk of the gene expression data generated using OPT within the emage database was for a detailed analysis of the gene-expression of the Wnt gene family and associated pathway genes (Vendrell et al 2009 DOI: 10.1016/j.gep.2009.03.001). The items in this collection include the 3D reconstructions of the original data and the mapped expression patterns in the context of the eMouseAtlas model embryos. The mapped data is provided as a single item to allow convenient download for viewing and further bioinformatics analysis.