"Humans are truly a complex array of organs and other tissues designed to support the basic functions and vitality of our body. We are able to process inhaled air and ingested food and regulate body content. We selectively take what we need from the external environment and eliminate what we do not need. We think, move about, and reproduce. Many of these operations occur without us even being aware.One other term we should be familiar with is tissue. Quite simply, tissue is comprised of similar or cooperating cells performing similar or cooperative tasks. These cells may be grouped together to form fascinating tissues such as bone, skin, muscle, nerves, and blood."