The Yamanaka study —
why four factors are enough.
In 2006, a lab in Kyoto demonstrated that four factors are sufficient to fundamentally alter a cell's state. Not one hundred. Four. Here is what that means for how we think about skin quality — and what it explicitly does not.
The question behind the question
Skincare routines have grown longer in recent years. Seven steps, ten steps, twelve. Every step has a justification, every product an active ingredient, every ingredient a study. The logic behind it is additive: if you do more of the right things, you get a better result.
But skin does not behave additively. Many users find that the twelfth step is less effective than the third — and that phases with noticeably good skin often do not coincide with particularly elaborate routines, but rather with holidays, sleep, or a quieter month.
This points to a different question. Not: "What product is missing?" But: "Which few factors actually determine the state this skin is in?"
This way of asking is not an invention of the cosmetics industry. Its most precise expression was found in an experiment that has nothing to do with skincare.
What happened in the lab in 2006
Kazutoshi Takahashi and Shinya Yamanaka were working on a question that was considered largely settled: Can a mature body cell be turned back into an earlier developmental state? A skin fibroblast is a skin fibroblast. Its identity is determined not by the genes — they are the same in every cell — but by which genes are read and which remain silent.
The research group started with twenty-four candidate genes typical of the embryonic state and systematically reduced them. In the end, four transcription factors remained. When introduced in combination, they transformed mouse fibroblasts into a pluripotent state: induced pluripotent stem cells.1 A year later, they achieved the same with adult human skin fibroblasts — using the same four factors.2 In 2012, they were awarded the Nobel Prize in Medicine.
A central regulator of the pluripotent state. Without it, the combination does not work.
Works in tandem with Oct3/4 and stabilizes the achieved state.
Opens up densely packed chromatin regions and keeps the cell alive during the process.
Accelerates cell division and transcription processes. It is also the most problematic of the four — c-Myc is a proto-oncogene.
Why the number isn't the lesson
It would be tempting to cling to the number four. That would be a misunderstanding. The fact that there are four, and not three or six, is a finding of molecular biology, not a law of nature. Other groups later worked with three factors, with chemical substitutes, with different combinations.
The lesson is structural — and therefore transferable.
A complex state is rarely determined by the sum of all influences. It is determined by a few dominant factors. If you know these factors, you don't need a list of a hundred entries. If you don't know them, a list of a hundred entries won't help you either.
Before 2006, the prevailing assumption was that the state of a differentiated cell was the result of countless interlocking factors — too many to sort. The real achievement of the experiment was not the reprogramming itself. It was the proof that a short list hides behind apparent complexity.
It is not the number of influences that determines a state, but which few dominate it.
What this does not mean for skincare
At this point, precision is more important than enthusiasm, as the term is increasingly being used loosely in the cosmetics market.
The four factors are transcription factors. They work in the cell nucleus and are introduced into the cell in the lab via viral vectors or mRNA. They are not contained in any cosmetic product, and they cannot be — neither in this nor in any modified form. A topically applied product does not reach the cell nucleus in this way, and an intervention in gene expression would, by definition, no longer be a cosmetic product.
Even within research, full reprogramming is not the goal. A cell that completely loses its identity is worthless to a tissue and potentially dangerous. The work of recent years has therefore focused on partial and transient reprogramming: short, controlled expression where markers of aging change, but cell identity is preserved.3,4,5 This is basic research on cell cultures and animal models. It is not an application, not a product, and not a statement about skin in the bathroom.
Phrases to be wary of
Such phrasing transfers laboratory results to a product without any mechanism for such a transfer existing. They are not permitted as cosmetic performance claims in the EU and are factually indefensible. Where they appear, the reference to research is merely decorative.
Addition has costs
Additive logic is not just inefficient. It is not free.
Experimental models of cumulative irritation show that repeated, individually mild effects add up in their impact on the barrier function — measurable via transepidermal water loss.6 Each single application remains unnoticeable. The sequence does not.
Dermatological literature has now explicitly addressed this pattern for contemporary skincare routines: cumulative exposure to active and potentially sensitizing ingredients, use outside of appropriate indications, and expectations shaped by social media are described as factors for irritant and allergic contact reactions.7
- Asks what determines the state
- Measures effort by whether the relevant factor is addressed
- Multiple observations can be traced back to the same factor
- Lack of effect means: factor wrongly identified
- Asks what else can be added
- Measures effort in steps and products
- Every problem gets its own product
- Lack of effect means: more of the same
The practical difference is visible in how one deals with stagnation. In additive logic, a lack of results is an argument for another product. In factor-based logic, it is an indication that the cause lies elsewhere — and that another product will change nothing.
The four factors behind skin quality
NATURFACTOR organizes influences on skin quality into four areas. The analogy to cell biology lies exclusively in the logic of thinking: reduction to what actually dominates a state. There is no substantive connection between these four factors and the four transcription factors — nor is any claimed.
External influences: UV radiation, humidity, temperature, season, air quality, travel, heating air. Guiding question: What influences is this skin exposed to?
The conditions for regeneration: duration and quality of sleep, stress, recovery phases, physical exertion. Guiding question: How well can this skin recover?
Chronobiological processes: differences between day and night, regularity, cyclic changes in skin condition. Guiding question: Does this routine work with the skin's rhythm?
Targeted support through formulation and application: active ingredients, textures, frequency, order. Guiding question: How is this skin being supported?
Care is one of four. Not the least important — but also not the factor that compensates for the other three. A formulation can support the skin in an environment. It cannot replace the environment. It can accompany the nightly regeneration phase. It cannot manufacture it.
What follows from this
This principle does not lead to a product. It leads to a sequence.
First, the assessment: Which of the four areas are actually burdened for this skin, in this month? Someone who sleeps little and travels a lot for weeks will not find the answer in an additional serum. Someone who has solid regeneration and lives in stable environmental conditions will achieve more with Care than someone else with the same product.
Then, the reduction: Which single factor is the dominant one? In most cases, it is one; occasionally two. Addressing four simultaneously is again additive thinking, just with better vocabulary.
And finally, the patience to attribute the effect to the factor and not to chance. Skin quality changes in weeks, not days. A change that appears after three applications is rarely what it is thought to be.
The question is not how many products a routine needs. The question is which factor is currently determining this skin — and whether the routine actually addresses it.
This article puts scientific contexts into perspective and does not replace dermatological advice. In the case of persistent skin changes, severe irritation, or unclear findings, medical evaluation is indicated. Cosmetic products are intended for the care and support of the skin.
Frequently Asked Questions
Are the Yamanaka factors contained in skincare products?
No. These are transcription factors that are introduced into cells in the lab via viral vectors or mRNA. They are not contained in any cosmetic product, and a topically applied agent does not reach the cell nucleus in this way. Product claims suggesting a connection are untenable.
Why exactly four factors in the NATURFACTOR framework?
Because influences on skin quality can be sensibly organized into these four areas without any essential area being missing or two areas overlapping. The number is not a quote from cell biology. What is adopted is the principle of reduction, not the number.
Does this mean fewer products are fundamentally better?
Not fundamentally. It means the number of products is not a meaningful metric. Three products that do not address the dominant factor are less effective than one that does. Cumulative irritation, however, is a documented phenomenon — the number of steps is not neutral.
What is partial reprogramming?
A research approach where reprogramming factors are expressed only briefly and in a controlled manner so that markers of aging change, but the cell retains its identity. Work on this is conducted on cell cultures and animal models. This is basic research and has no application-related relevance to skincare.
- Takahashi K, Yamanaka S. (2006). Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell, 126(4), 663–676.
- Takahashi K, Tanabe K, Ohnuki M, et al. (2007). Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell, 131(5), 861–872.
- Ocampo A, Reddy P, Martinez-Redondo P, et al. (2016). In vivo amelioration of age-associated hallmarks by partial reprogramming. Cell, 167(7), 1719–1733.e12.
- Gill D, Parry A, Santos F, et al. (2022). Multi-omic rejuvenation of human cells by maturation phase transient reprogramming. eLife.
- Su Y-R, Gu S-M, Liu Y-R, et al. (2023). Partial cellular reprogramming stably restores the stemness of senescent epidermal stem cells.
- Gabard B, Elsner P, Treffel P. (1996). Barrier function of the skin in a repetitive irritation model and influence of 2 different treatments. Skin Research and Technology.
- van der Bent SAS. (2025). The skincare routine: hype or hidden harm?
