Diagnostic tests for diseases like Zika or Ebola are often very specific in what they measure and don’t always work for local populations. That’s why researchers have designed a Lego-like kit designed to make it possible for technicians anywhere to make, and tweak, diagnostics themselves. The tiny kit uses modular blocks that can be connected in different patterns to replicate the function that would typically be built into a manufactured test. With the kit, no lab is needed, and the test costs $1.