A new prototype petri dish can create an image of what’s growing on it and send that information to a laptop, all from inside an incubator. The prototype, dubbed the ePetri, was created from Lego blocks and a cell-phone image sensor, and uses light from a Google Android smart phone.

“Normally, one leaves the cells in an incubator and just checks up on them from time to time,” says Michael Elowitz, a professor of biology at Caltech, who coauthored the paper. “With ePetri, it’s like getting continuous tweets from the cells rather than an occasional postcard.”

A sample is placed on top of a small image-sensor chip, which uses an Android phone’s LED screen as a light source. The whole device is placed in an incubator, and the image-sensor chip connects to a laptop outside through a wire. As the image sensor snaps pictures of the cells growing in real time, the laptop stitches hundreds of images together to create a high-resolution picture of what is happening on the dish.

The resolution is similar to a traditional microscope—fine enough to see the contents of cell nuclei, says senior author Changhuei Yang, professor of electrical engineering and bioengineering at Caltech. The prototype was described in a paper appearing online this week in the Proceedings of the National Academy of Sciences.

Peering into cells while they stay in the incubator has a number of benefits. For one, each device is its own lens-free microscope, meaning that many samples can be monitored at once automatically on the laptop. In addition, instead of using a microscope that can only focus on one tiny part of a sample, researchers get a picture of what’s happening on the entire petri dish at the same time—something that would help a lot with stem cells, which often change into different types of cells and move around.

The team is also working on a self-contained system with its own incubator that could eventually stay as a desktop diagnostic tool in a doctor’s office, so bacterial samples wouldn’t have to be sent out to a lab for testing.

“The low cost allows you to think creatively about how this will be used in the future,” says Jeffrey Morgan, a professor at Brown University who was not involved in the study. For example, the new device could cut down on time and cost for high-throughput drug screening, and create cheaper diagnostic tools.