Bacteria are so small that 350 would fit in a line across the full-stop at the end of this sentence. Despite their size, many bacteria carry out beneficial or co-operative social interactions, with only a few being pathogenic murderers! Without bacteria, in the broadest sense, there would be no life on earth. My work concerns predatory bacteria; these invade and kill pathogens naturally, like living antibiotics. Studying their bacterial lives teaches humans how to combat drug-resistant infections. It also displays the beauty and complexity of the microscale architectures, and behaviours of a hidden world of tiny cells, that support us humans.