 Your choice of microcontroller generally determines the amount of flash, RAM, or EEPROM you have to work with. However, you can add external storage for data and files. You can find memory breakout boards for flash chips, SD cards, EEPROM, or even exotic F-RAM storage. They all use standard I2C or SPI comms, so connections are simple and familiar, like adding another sensor to your project. This specific board has 256 kilobytes of ferroelectric RAM, or F-RAM, on board, which supports fast reads and writes like common S-RAM, but is also non-volatile, retaining data when unpowered, like flash or EEPROM. This makes F-RAM a particularly versatile, best of both worlds option for logging data. All it's missing is the capacity and removable of an SD card. But hey, nobody's perfect.