Abstract: Function-specific homeostasis (FSH) is a negative-feedback response of a biosystem to maintain the function-specific fluctuations inside the biosystem so that the function is perfectly performed. A stress is also a function of a biosystem. A FSH-specific stressor (FSSR) is so defined that it disrupts the FSH. A FSH-specific stress (FSS) of a biosystem is defined to be a response of the biosystem to a FSSR and may also be in FSS-specific homeostasis (FSSH) in which a FSS disrupt FSH1 but establish FSH2 so that it is called successful stress. There is FSH/FSSH-specific sirtuin 1 (SIRT1) activity (FSSA1). SIRT1 is nicotinamide adenine dinucleotide (NAD+) dependent, but NAD+ is limited by nutrition. A FSS increases SIRT1 activity so that FSSA1 is locally minimum. A person might simultaneously have many kinds of FSH, FSHi, i = 1, 2, , n, each of which has quality Q, Qi, i = 1, 2, , n. Let Qmax = maxQi, i = 1, 2, , n and the corresponding function is Fmax. The best structure of Q is a pyramidal hierarchy in which Qmax is at its peak but the other Qs are as low as possible if Fmax can be optimized.