UV stops in epidermis; red (620-700nm) reaches 2-5mm; NIR (800-1100nm) penetrates subcutaneous tissue and muscle at 5-40mm.
A free, animated wavelength vs tissue penetration depth you can read here or embed on any website, from Scrollchart.
Wavelength vs Tissue Penetration Depth
Not all wavelengths of light penetrate tissue equally. Short wavelengths (UV, blue) are absorbed in the epidermis and very superficial dermis by melanin, hemoglobin, and DNA. Longer wavelengths in the red and near-infrared (NIR) range encounter less absorption and more scattering, allowing them to reach deeper structures.
The therapeutic window for photobiomodulation (PBM, also called LLLT) spans approximately 620-1100 nm. Red light (620-700 nm) reliably reaches the dermis and superficial muscle at 2-5 mm. NIR (700-1100 nm) penetrates 5-40 mm and can reach subcutaneous fat, deep muscle, and even superficial joints.
At therapeutic wavelengths, the primary photoacceptor in cells is cytochrome c oxidase (Complex IV of the mitochondrial electron transport chain), which has absorption peaks in the red (~620-680 nm) and NIR (~760-940 nm) ranges. Photon absorption increases electron transfer efficiency, raises mitochondrial membrane potential, and increases ATP production and nitric oxide release.
Secondary effects include modulation of reactive oxygen species (ROS), activation of redox-sensitive transcription factors (NF-kB, Nrf2), and upregulation of growth factors (VEGF, TGF-beta). These downstream effects account for reported benefits in wound healing, inflammation, pain, and muscle recovery.
Good for
Red-light therapy device explainer pages
Photobiomodulation protocol articles
Dermatology and wound-healing content
Sports recovery device marketing
Source & accuracy
Hamblin MR, Photobiomodulation reviews; Wan S et al., J Invest Dermatol 1981 (penetration data)
Why longer wavelengths reach deeper
How far light travels into skin and tissue depends largely on its wavelength. Shorter wavelengths are strongly absorbed and scattered near the surface, so ultraviolet light is mostly stopped in the outer layers of the epidermis. As wavelength increases through the visible range, absorption by pigments and water eases and scattering falls, so the light reaches progressively deeper. Red light in the roughly 620 to 700 nanometre range reaches into the dermis, on the order of a few millimetres.
Near-infrared light, around 800 to 1100 nanometres, sits in a relative optical window where penetration is greatest before water absorption rises again at longer wavelengths.
How depth estimates should be read
Penetration figures are approximate and depend heavily on skin tone, blood content, hydration, and how depth is defined, so quoted values such as a few millimetres for red or up to a few centimetres for near-infrared describe ranges rather than fixed cut-offs. Pigment and blood absorb strongly, which is one reason results differ between people.
This is general educational information about tissue optics, not medical advice or a claim that any light exposure treats a condition; clinical use of light should follow qualified guidance.
Embed this diagram
Add this animated wavelength vs tissue penetration depth to your own site. Copy one line of HTML, or use the embed builder for theme and sizing options.
Reference
What this is
A free, embeddable, animated wavelength vs tissue penetration depth for any website.
Who uses it
Medical educators, Health blogs, Biohacker blogs, Wellness sites.
How to embed
Copy one line of HTML. No signup. No watermark. Works in WordPress, Webflow, Ghost, Substack, plain HTML.
File size
iframe embed, ~80 KB gzipped (loads on demand, does not block your page paint).
License
Free forever. Editorial explainer text included; updated centrally over time.
Copy the universal HTML snippet, the WordPress shortcode, or an iframe fallback -
see the WordPress plugin page for details. Any format keeps
the same Core Web Vitals profile and the same explainer text.
By embedding, you acknowledge the diagram and explainer text are served from scrollchart.com and may be updated from time to time to reflect new research or to link to relevant sources within the explainer.
Frequently asked questions
Where can I get a free animated "Wavelength vs Tissue Penetration Depth" for my website?
Scrollchart provides "Wavelength vs Tissue Penetration Depth" as a free, embeddable animated diagram you can add to any website with one line of HTML. No signup is required and there is no watermark. The diagram and its explainer text are served from scrollchart.com, so the embed stays current without any maintenance on your end.
How do I embed a wavelength vs tissue penetration depth diagram in a health or wellness blog?
Copy the HTML snippet from the Scrollchart diagram page and paste it into any post or page in your CMS. It works in WordPress, Webflow, Ghost, Substack, and plain HTML without any plugin or account. The diagram renders as animated SVG directly in your page, so search engines can index the accompanying explainer text.