The discovery of the Higgs boson in 2012 marked a milestone in particle physics, enabling detailed studies of its properties. Among these, the search for new sources of CP violation in the Higgs sector is particularly compelling, as it could help explain the universe's matter-antimatter asymmetry. The ttH and tH production processes offer a unique window into the CP properties of the top-Higgs interaction, allowing direct measurements of this coupling without contributions from virtual loops. In this presentation, I will share my PhD work on the first measurement of the CP nature of the top-Higgs coupling in the ttH (H→bb) channel, using data collected during Run 2 by the ATLAS experiment.