If this is allowed to happen, tissue repair cells such as macrophages, fibroblasts, and blood vessel cells penetrate into the fibrinous adhesion and lay down collagen and other matrix substances to form a permanent fibrous adhesion. In 2002, Giuseppe Martucciello's research group showed a possible role could be played by microscopic foreign bodies (FB) inadvertently contaminating the operative field during surgery.[3] These data suggested that two different stimuli are necessary for adhesion formation: a direct lesion of the mesothelial layers and a solid substrate foreign body (FB).