The networked sensor regime is an exciting new design space that is emerging as a result of innovations in RF Communication technology and MEMS technology. TinyOS explores the software support that is required in that design space. TinyOS is a component-based runtime environment designed to provide support for deeply embedded systems, which require concurrency intensive operations while constrained by minimal hardware resources. For example, originally designed for the Smart Dust hardware platform, our scheduler fits in under 200 bytes of program memory.