re either measured in micrometres (one millionth of a metre), or millimetres (one thousandth of a metre). We review three classes of 'microdevice', 'Memory Spots 'motes' (being developed in the US as a result of various 'smart dust' projects) and the Hitachi Mu chip (an ultraminiaturised RF ID device). Two of these devices have failed to gain market traction for reasons that we need to analyse. All three device classes are, or were, intended to store information and/or collect information and/or provide identification. All of them are, or were, communication devices. A particular interest is to consider how we communicate with these communication devices and whether the cellular phone has a valid role in this communication process. We compare these microdevice applications with a present larger form factor application (contactless smart cards) and suggest some technical and commercial commonalities. We dis- cuss the present status of 'phone to device' communication systems, particularly RF systems and protocols and question whether there are plausible cellular phone and mobile broadband business models to justify development investment in this intriguing but challenging applica- tion sector. We highlight certain factors that suggest adoption time scales may be longer than commonly supposed. Making Telecoms Work: From Technical Innovation to Commercial Success, First Edition. Geoff Varrall. © 2012 John Wiley & Sons, Ltd. Published 2012 by John Wiley & Sons, Ltd. Making Telecoms Work Microdevices - How Small is Small? MEMS and microminiaturisation techniques in combination with silicon geometry scaling are allowing us to deliver storage functionality, information gathering functionality, identification and communication capability in increasingly small devices. Table 19.1 lists three form factors ranging from a grain of rice (small) to a grain of sand (very small) to a grain of dust (very very small). A grain of dust typically has a diameter of a few tens up to 200 or 300 micrometres, hence the term 'microdevice'. 