This experimental study asks whether custom solid microstructures can be fabricated directly inside living cells. The authors microinject photoresist into HeLa cells and use two-photon polymerization to print approximately 10-micrometer structures, including graphical barcodes and diffraction gratings. Separate whole-droplet single-photon curing produces intracellular microlasers. Confocal imaging and electron microscopy characterize the structures, and cellular observations show division and altered division times. The method is a proof of concept in individually handled cells; injection and

What if a cell could contain a structure we designed?

Researchers used focused light to 3D-print tiny objects directly inside living cells. An elephant is only the beginning.

A physical tool inside a biological system.

Don’t put it in. Build it there.

Getting a solid, micrometer-sized object into a cell is difficult. Many cells cannot swallow something that large.

This work takes another route: inject a liquid ingredient, then use light to solidify only the parts you want. A laser’s tiny focus traces a three-dimensional design inside a droplet, inside a living HeLa cell.

Unexposed liquid gradually dissolves. The solid structure remains in the cell’s interior—the cytosol.

Make something smaller than a cell.

Move through the experiment, from a liquid droplet to a free-standing object.

Start with a liquid resin droplet

01 / A 10–15 μm resin droplet is injected into the cell.

Light becomes a tool

The near-infrared beam travels through the cell. Only at its tightly focused point is the intensity high enough for two-photon polymerization: liquid resin becomes solid.

A shape, layer by layer

The focal point follows a designed path, building from the top downward. A typical 10 μm object takes 3–10 seconds of exposure; preparation and alignment take longer.

The surrounding liquid goes

Over the next few hours, the unpolymerized resin dissolves. The printed object stays inside. This sequence compresses those distinct timescales.

Yes, the elephant is really inside.

Explore the original figures. Confocal cross-sections show the membrane covering the object; electron microscopy reveals its structure.

Figure 1 · The printing method. A resin droplet is injected, selectively polymerized and dissolved. Confocal cross-sections in panel e show the cell membrane covering the printed elephant.

Original figures: Mur et al., Advanced Materials (2026), CC BY 4.0. Reproduced without content changes; resized for display. Tap the image to enlarge it.

Thin walls measured in resin droplets in a glycerol–water mixture with a cell-like refractive index.

Surviving cells divided, passing the structure to one daughter cell. Large structures extended division by one to a few hours.

After 24 hours, the reported nonviable fractions were 55% for cells with printed structures, 50% for a control injection of dyed medium, 44% for silicone-oil injection and 10% for untreated controls. Figure 2 also accounts for cells lost during medium exchange. The authors identify membrane penetration as a major contributor and discuss further optimization of materials, injection and handling.

Read a shape with light.

A printed grating makes a pattern of bright spots. Its geometry becomes an optical signature that can be read from outside the cell.

SIMPLIFIED RECIPROCAL-SPACE GEOMETRY · ILLUSTRATIVE, NOT A MEASUREMENT

Square symmetry produces a square arrangement of spots. Wider grating spacing brings the spots closer together.

Change the object. Change the signal.

Rotate the grating and the diffraction pattern rotates with it. Increase its spacing and the bright spots move inward. The paper demonstrates square and hexagonal gratings in cells, and proposes using their orientation-dependent signatures to read cellular rotations.

From tiny sculptures to intracellular tools.

An identity for a cell

A four-layer, three-dimensional barcode encodes 61 bits—about 2 × 10¹⁸ possible codes. Unlike random tagging, its information can be designed in advance.

A light-emitting device

The team also made 9 μm microlasers by curing whole droplets of a different resin with one-photon UV light. These were separate from the patterned two-photon prints.

Tools that act from within

Custom sensors, mechanical elements, compartments and drug-delivery structures could bring new ways to study or influence a cell’s interior.

The larger idea: give a living cell a designed physical structure—and explore what that makes possible.

Two‐Photon 3D Printing of Functional Microstructures Inside Living Cells

Maruša Mur, Aljaž Kavčič, Uroš Jagodič, Rok Podlipec & Matjaž Humar

Advanced Materials · 2026 · DOI: 10.1002/adma.202519286