  The Loop-Tree Duality (LTD) theorem is an innovative technique to deal with
multi-loop scattering amplitudes, leading to integrand-level representations
over an Euclidean space. In this article, we review the last developments
concerning this framework, focusing on the manifestly causal representation of
multi-loop Feynman integrals and scattering amplitudes, and the definition of
dual local counter-terms to cancel infrared singularities.
