This right here is the world’s smallest certified Bluetooth module(EYSHSNZWZ) from Taiyo Yuden. With a size of 3.25mm x 8.55mm x 0.85mm, it’s really tiny. The pic below shows it next to a Basmati rice grain. Its Bluetooth 5 compatible, Nordic nRF52832(WLCSP package) chip with ARM Cortex M4F(512KB Flash/64KB RAM). Its entirely certified for FCC, Japan, China and EU usage for wireless plug-and-play. Reduces the headache of certification and antenna performance. One of the best choices out for tiny wearable modules. Scared to use this on a project. Hopefully won’t misplace this one. 😀
PS: Have also added an internet mandatory image next to a banana for scale.