This does get into some very technical details - but some people do want a detailed explanation for nail peeling or brittleness...
Nail Plate Composition
The nail plate is the hard part of the nail that grows out and is composed of three primary layers (but actually a much larger number of layers) of compacted dead cells (dorsal, intermediate and ventral nail plates). Without getting TOO technical the "toughness" of the nail plate relates to the alignment of the keratin fibers and to disulfide cross-links.
Why do Nails Peel?
To really simplify the reason for nail peeling - the bonds between the layers of nails break and the nail layers are able to peel.
Although there can be medical reasons for peeling nails - usually the cause is the result of a series of drying out and then wetting of the nails and then drying out etc. Without a proper protective layer on the nail plate it can dry out (especially in dry conditions like winter or in a hot dry climate). Repeated exposure to chemicals, nail polish, acetone nail polish remover and even just water can also help cause the issue. The repeated cycle eventually allows the different layers to separate from each other.
What to do?
You could avoid: taking long baths; washing hands; using hand sanitizer; doing dishes without gloves or applying nail polish and using acetone nail polish remover. All these things (and more) strip out protective elements of the nail plate and lead to the nail plate drying out which leads to peeling or brittle nails. Add to this very dry air that can at times be part of just normal weather conditions and MOST people will not change enough of these type of things to dramatically improve nail conditions.
How to Overcome
A simple 20 second a day application of FlexiNail will help improve and protect the nail plate composition - even considering harsh outside influences. Helping prevent the cycles of drying out and rehydration of the nail will help prevent nail peeling. It also will not hurt at all if you can minimize or lessen the number of times you apply and remove nail color and use acetone remover (as this is really hard on the nail plate).
If you are still reading... then you are REALLY interested in the human nail. The main chemical composition of the nail is keratin. There are alpha-keratin (helical) filaments and cystine rich (non-helical) keratins. The nail contains different amino acids and bunch up to form polypeptide chains in the keratin. There are covalent disulfide cross-links and linkages that are said to be responsible for nail hardness. In addition to these disulfide cross links there are also secondary bonds (polar linkages, peptide linkages, hydrogen linkages etc) within the keratin structure. All of this contributing to the unique structure of the nail. The water content of the nail has also been shown to be around 15 to 18% and plays a role in the flexibility or elasticity of the nail. When we expose our nails to harsh conditions and chemical this can alter and damage the nail structure and lead to problem nails. Help your nails with a simple 20 second application of FlexiNail daily and you will be rewarded with stronger nails you can be proud of.