A light emitting diode (LED) assembly comprising a LED module that comprises at least one LED, and a high voltage circuitry , e.g. 230 VAC drive circuitry, to receive power supply from a high voltage source and to convert and supply energy to drive said at least one LED, said LED module has a flat and thin extension with a height H in the range of 5-20 mm in a direction corresponding to the main direction of light to be emitted from said at least one LED, said LED assembly comprises: - a connector unit provided with connector pins , and a functional module receiving recess shaped and structured to receive and releasably attach a functional module by mechanical cooperation with attachment members of said functional module , said recess is shaped and structured such that said connector pins are positioned to be connected to connecting members of said functional module , characterized in that said LED assembly further comprises: - a set of at least two functional modules , each functional module within the set has a unique functionality, wherein all functional modules of said set have identically shaped module housings provided with attachment members , and connecting members being configured to receive supply energy from said LED module , and to establish bi-directional communication between said LED module and said functional module when attached to said LED module, wherein said module housing has a flat configuration having a predetermined maximum height, a width and a length, and wherein said receiving recess is shaped and structured such that the plane of said functional module , when attached to the connector unit , is essentially parallel to the flat extension of said LED module , such that said functional module does not shadow the light, and wherein said connector unit is arranged such that it is available on a side of the LED module of the main direction of light to be emitted from said at least one LED, enabling the functional module to be attached when the LED module is mounted to e.g. a wall. - a connector unit provided with connector pins , and a functional module receiving recess shaped and structured to receive and releasably attach a functional module by mechanical cooperation with attachment members of said functional module , said recess is shaped and structured such that said connector pins are positioned to be connected to connecting members of said functional module , - a set of at least two functional modules , each functional module within the set has a unique functionality, wherein all functional modules of said set have identically shaped module housings provided with attachment members , and connecting members being configured to receive supply energy from said LED module , and to establish bi-directional communication between said LED module and said functional module when attached to said LED module, wherein said module housing has a flat configuration having a predetermined maximum height, a width and a length, and wherein said receiving recess is shaped and structured such that the plane of said functional module , when attached to the connector unit , is essentially parallel to the flat extension of said LED module , such that said functional module does not shadow the light, and wherein said connector unit is arranged such that it is available on a side of the LED module of the main direction of light to be emitted from said at least one LED, enabling the functional module to be attached when the LED module is mounted to e.g. a wall. <EOS>