The treatment of blood-related diseases often relies on hematopoietic stem cell (HSC) transplants. However, many patients struggle to find a compatible donor. The ultimate goal of regenerative medicine is to create an alternative source of HSCs but generating fully functional HSCs in vitro remains challenging. A groundbreaking discovery revealed that embryonic stem cells can self-organize into embryo-like structures named gastruloids. In this proposal, we will investigate whether gastruloids can replace the use of embryos to study the early steps of HSC formation and serve as a novel platform for producing transplantable HSCs for future clinical use.