Scientists have developed a low-cost and easy-to-use smartphone attachment that can quickly and accurately evaluate semen samples for at-home fertility testing, providing a potentially helpful resource for the more than 45 million couples worldwide who are affected by infertility. It is estimated that male infertility plays a role in roughly 40% of those cases, underscoring a need for more routine and reliable semen analysis testing. Existing clinical protocols that measure semen quality require highly trained technicians to operate expensive and specialized equipment, and are slow to return results. In search of a better assay, Manoj Kanakasabapathy and colleagues created a portable device that quantified sperm concentration and motility in seconds, using the processing power and camera found in widely-available smartphones. The platform, which the researchers dubbed Fertilex, was assembled for a total materials cost of $4.45, an inexpensive alternative to standard-of-care methods. Testing semen with Fertilex required only six simple steps to successfully measure sperm concentration, motility and total sperm count from undiluted and unwashed samples. What's more, Fertilex was so user-friendly that 10 volunteers with no formal training - including administrative assistants recruited from a Boston fertility clinic - correctly classified more than 100 semen samples. Kanakasabapathy et al. analyzed 350 specimens, demonstrating that the platform could detect abnormal semen with either insufficient sperm concentrations or low levels of motility (according to World Health Organization Guidelines) with greater than 95% accuracy. The authors say the smartphone-based fertility test could be used by men to monitor their semen at home after undergoing vasectomies, or as a point-of-care diagnostic tool in developing countries.