research (do not read, I just need to read it and have a copy of my own)

A young/prime adult, according to Erik Erikson's stages of human development, is generally a person aging from 20 to 40. Young/prime adulthood can be considered the healthiest time of life'[12] and young adults are generally in good health, subject neither to disease nor the problems of senescence. Biological function and physical performance reach their peak from 20–35 years of age.
Young Adulthood Stages of Development
Physical development for the young adult typically sees one in the best physical condition: strong, sharp senses, and stamina. Memory and thinking (cognitive) abilities are at their highest.
The social development and personality development for the young adult can be identified with a desire to be socially independent and with a high ambition to succeed and can include occupation selection, selecting a life-partner, starting a family, accepting responsibilities, and social networking. (Nevid & Rathus, 2005)

Middle age is the period of age beyond young adulthood but before the onset of old age. usually considered to occur approximately between the ages of 40 and 60. Middle-aged adults often show visible signs of aging such as loss of skin elasticity and graying of the hair. Physical fitness usually wanes, with a 5–10 kg (10-20 lb) accumulation of body fat, reduction in aerobic performance and a decrease in maximal heart rate. Strength and flexibility also decrease throughout middle age. However, people age at different rates and there can be significant differences between individuals of the same age.[1] Both male and female fertility declines with advancing age.
Middle Adulthood Stages of Development
The physical development in middle adulthood can be accompanied a loss of strength, vision sharpness, strength, and coordination. Cognitive development during middle adulthood generally shows an average memory loss and a reduced ability to perform tasks requiring speed. The social and personality development during middle adulthood is considered by some to be synonymous with "mid-life crisis" which heralds the reevaluation of one's life goals and accomplishments and can spur positive changes, not just the negative changes generally associated with mid-life crisis and greater psychological health. (Nevid & Rathus, 2005)

. Old age can cause, amongst other things:
 Wrinkles and liver spots on the skin due to loss of subcutaneous fat
 Change of hair color to gray or white
 Hair loss
 Reduced circulatory system function and blood flow
 Reduced lung capacity
 Reduced immune system function
 Changes in the vocal cords that produce the typical "old person" voice
 Lessened and weakened hearing. Of individuals 75 and older, 48% of men and 37% of women encounter difficulties in hearing. Of the 26.7 million people over age 50 with a hearing impairment, only one in seven, a meager 14 percent, use a hearing aid
 Diminished, and decline in eyesight. It becomes more difficult to read in low lighting and in smaller print. Speed with which an individual reads may also be impaired.
 Reduced mental/cognitive ability.
 Depressed mood
 Lessening or cessation of sex, sometimes because of physical symptoms such as erectile dysfunction in men, but often simply a decline inlibido also known as sex drive.
 Greater susceptibility to bone and joint diseases such as osteoarthritis and osteoperosis
 Memory Loss is common due to the decrease in speed of information being encoded, stored, and received. It may take more time to learn new information.
Alzheimer's disease, the most common form of dementia, is found in old age. It is a general term for memory loss and other intellectual abilities serious enough to interfere with daily life. Alzheimer's disease accounts for 50 to 80 percent of dementia cases.

According to Erik Erikson’s "Eight Stages of Life" theory, the human personality is developed in a series of eight stages that take place from the time of birth and continue on throughout an individual’s complete life. He characterises old age as a period of "Integrity vs. Despair", during which a person focuses on reflecting back on their life. Those who are unsuccessful during this phase will feel that their life has been wasted and will experience many regrets

Assistance and Care
According to the Journal "Demography", there is a rise in the elderly living alone if not with a spouse. Individuals 75 and older have decreased in amount needing help taking care of themselves. Many new assistive devices made especially for the home have contributed greatly to this. Some examples of devices are a shower seat (making it so the person does not get tired in the shower and fall), a bed cane (offering support to those with unsteadiness getting in and out of bed), and an ADL cuff (used with eating utensils for people with paralysis or hand weakness).
However around 25% of individuals 85 and older say that they need help with their activities of daily living. There are many options for long term care to those who require it. There is home based care where a family member, volunteer, or trained professional will aid the person in need and help with daily activities. Another option is community services which can provide the person with transportation, meal plans, or activities in senior centers. A third option is assisted living where 24 hour round the clock supervision is given with aid in eating, bathing, dressing, etc. A final option is a nursing home which provides professional nursing care.

Late Adulthood Stages of Development
Late adulthood can be marked by menopause and osteoporosis, a reduction in bone density, grey hair, less skin elasticity, and a loss of muscle mass resulting in an increase of body fat. Cognitively, during late adulthood verbal skills such as vocabulary and broad-spectrum knowledge are retained, but memory and mobility tends to decrease. Social and personality development can be affected by many variables during late adulthood: individuals in late adulthood may experience depression that may go untreated, and an individual in late adulthood may experience a period of readjustment to changes in their body, retirement, financial status change, and loss of a spouse. (Nevid & Rathus, 2005)