 Multiple myeloma, millimetre, is a cancer of the plasma cells found in the bone marrow. Recent research has revealed that the bone marrow environment plays a key role in the development and progression of millimetre. This includes the stromal cells, osteoblasts, osteoclasts, endothelial cells, and immune cells, as well as the extracellular matrix and the liquid melior. These components interact with the malignant plasma cells, allowing them to home to the bone marrow and form tumours. Additionally, the presence of these components in the bone marrow prior to the formation of tumour cells has been termed the pre-metastatic niche, which may explain why some patients develop metastases while others do not. Understanding the interactions between the malignant plasma cells and the bone marrow environment could lead to improved treatments for millimetre. This article was authored by S. Mania, A. Sacco, X. Lelew, and others.