The creation of BLT humanized mice involves several steps. Firstly, immunodeficient mice, such as the NOD/SCID or NSG strains, are used as hosts. Human fetal liver and thymus tissues are implanted under the kidney capsule of these mice. Following this, the mice are injected with CD34+ hematopoietic stem cells derived from the same fetal liver. Over time, these human cells engraft and differentiate, establishing a functional human immune system in the mouse.