Science vs. superstition.

Its the very same process that gives us life and at the same time it also is the same process that is slowly killing us at the cellular level due to the bio-chemical process involved. We more commonly call this the process of physical aging, getting old or as some others of us might have it "getting long in the tooth".
Every individual cell in our body that is still living has its own tiny power plant for producing energy. Our bodies are the constituents of all these individual cells. They collectively form our various internal organs, muscles and body parts that allow our bodies to actually function and interact within our physical environment. The cells become specialized and know what parts to form via primed dna coding.
Its believed that all multi-cellular complex creatures originated from one ancestral single celled creature. Even more strangely is the supposed hap-hazard way in which it all apparently happened and came to be.
The story goes that a particular single celled creature was happily minding its own business as a single celled creature in some bubbling puddle or pond millions of years ago. Then along came a parasite that was just looking for its next meal. This parasite invaded the single celled creature with the intention of just getting lunch and moving on. However it wasn't quite going to be the case as this occurrence then produced a symbiotic coupling that turned this into the joining of these two separate creatures into a single celled creature that was now able to manufacture its own chemical energy by converting sugars and oxygen.
As the host cell replicated itself through cell division it also replicated the parasite as if it was part of the host cell in this new chemical power producing symbiotic state and its apparently been like that for the past few millions of years ever since. This in turn gave rise pretty much every single multi-cellular biological animal and creature on this planet including humans. We call this ancient ancestral microscopic single celled creature Mitochondrion or (mitochondria in its plural form) and it still exists within every living cell of the human body today.

The problem...
The problem is that this cellular chemical energy production that keeps us alive also produces what we call "free radicals". They're the same free radicals that you always hear the ads for expensive skin care cream going on about. At the same time I'd be very weary as to how effective these expensive skin creams actually are as these creams are applied externally. The skin on the external surface that the cream is applied to is already for the most part dead meaning there isn't really any free radical damage to actually reduce. The idea is you want to protect the living skin cells underneath that are still alive and are being destroyed by free radical damage.
Free radicals are produced as mitochondria combine oxygen and sugar in order to produce this chemical energy through out our entire bodies. The unwanted byproduct of this chemical energy production is what damages our cells and the dna (Deoxyribonucleic Acid) coding contained within in them.
The cells dna coding tell the cell exactly what it needs to do in order to make more of itself as the old copies of itself cells naturally die off. So as the cell divides and replicates itself it also replicates the dna coding/instruction sets. As these free radicals damage the dna coding the damaged dna coding is also replicated and passed on as the cell divides again over and over to create new cells. As time goes on the cell becomes less able to replicate itself as accurately as it once originally had been able to due to the cumulative damage to the dna from the free radicals. This is what causes aging.
Currently the only way humans can extend their lives and unique genetic coding beyond the decay of the finite limitations imposed by cellular dna damage is to reproduce. Its at the point of conception that the unique genetic coding from a male and female is recombined to make new genetically coded and unique variants. This is also the point at which the clock is reset and the dna instruction sets are passed on to the next generation undamaged as the cycle of cellular decay is reset and starts over again with what we more commonly call a baby. Provided there aren't any undesirable mutations that could cause genetic related illnesses within the new recombined iteration of the dna everything should be fine. However the reality is there is always the slim chance something may go wrong in which case its always a good idea to try to do all the things that would help to avoid such a potential scenario. Today we even have dna blood tests that can help more accurately determine whether any genetic complications might occur for a couple trying for a baby.
Obviously beyond the genetic aspects many of us more often then not want to transfer elements of personality too due to our more complex outlooks and needs as shaped by our progressed mental capacities and an evolved society. This is obviously linked to desirable personality traits and characteristics which we more often then not achieve through the process of parental "socialisation" in the preliminary stages which basically just means general interaction between parents and offspring through conversation, day to day activities, play etc. So you might want to be careful who you pick to be your primary role model if you do actually plan on having any potential offspring. Such characteristic traits will more then likely transfer to the offspring as a foundation before they begin to shape and adapt their own behavioral quirks, personality traits and general character by themselves through their social peers, their own choice of role model(s) and ultimately self modification. This is obviously why its perfectly possible that children who have been adopted from a very early age will more often then not behave in a way that's in line with the way in which their foster parents socialized them despite the different origin of genetics.
Significantly reduced free radical damage found in a particular species of bird
The aging process is obviously not unique to human beings. However actual research has shown that there are a few rare instances within nature where particular animals suffer comparatively very little free radical cellular damage such as within particular species of turtles that can live for well over 100 years and rare birds. At present research is still ongoing as to how these animals are able to achieve such a biological state. But generally these anomalous or rare creatures that to some degree defy the process have extremely low heart rate bpm counts.
Stem cell research could also hold the key
There has also been a certain amount of research relating to stem cells. Stem cells are basically the cells from a developing fetus. Generally these types of cells are extracted for use long before anything that even resembles a baby is even formed but this isn't to say that the use of stem cells isn't a highly contentious issue. This in turn still makes it a highly regulated practice with very narrow exception for actual experimentation to further research within current official channels and guidelines. As mentioned earlier this is the point at which the dna of the cells are pretty much brand new and as near perfectly in tact as can be without free radical damage. Stem cells have the potential to become any kind of cell within the body. As far as I'm aware research into stem cells mainly centers around using them for repairing the kinds of damage that causes severe disability rather then trying to use them to negate, stop or reverse the process of physical aging. Prime examples of more standard reasons for ongoing research into stem cells is for the repair of damaged or severed nerve cells in order to restore mobility to victims suffering from physical paralysis or more efficient accelerated repair for serious physical injuries.
Out of the lab
In humans the best we can do in this day and age is to slightly reduce the damaging effects of the processes involved with this bio cellular energy production that causes physical biological aging. There isn't actually any way to reverse the process without altogether stopping the actual process that's making us live. Other then that its pretty standard stuff for trying to stay looking youthful. Eat healthily (as in actual digestable food that you put into your mouth and eat), stay hydrated by drinking actual water (as in H2O), moisturize, use high factor UV protection sun block cream, avoid being in direct sunlight for long periods at a time to avoid sun aging and generally avoid bouts of sleep deprivation where ever possible. Obviously things like regular excessive alcohol consumption, regular excessive recreational drug use and heavy smoking will also further accelerate the appearance of physical aging over any prolonged periods of use.