Abstract: I will present an overview of the International Axion Observatory (IAXO), which will be the most efficient axion helioscope to date. I will discuss its physics potential and present some recent work about its sensitivity to well motivated QCD axion models. I will also present new results on the IAXO sensitivity to axions produced in nuclear transitions in the sun. Some emphasis will be given to a scaled down version of IAXO, called BabyIAXO, whose construction is expected to begin soon at DESY, in Hamburg.