A 7-week-old infant

is brought to the emergency department for severe hypothermia. Such a small

child does not have enough muscle mass to produce heat through muscle tremors,

and at the same time, his body has a large surface area causing easier heat

loss. Newborns and infants have a special way of producing heat through

non-shivering thermogenesis using brown adipose tissue. What does the basic

structure of this tissue look like?