Intramembranous ossification is a process by which bone tissue forms directly from mesenchymal tissue, which is a type of connective tissue. This method primarily occurs in the development of flat bones, such as those in the skull and clavicle. During this process, mesenchymal cells differentiate into osteoblasts, which are cells that produce bone matrix. Unlike endochondral ossification, where bone replaces cartilage, intramembranous ossification does not involve a cartilage stage. Instead, the bone develops within a membrane, leading to the formation of spongy bone that can later be remodeled into compact bone. This process is crucial for the proper formation of certain bones in the human body.