These individually-addressable RGBW LED strips are great for all sorts of uses: custom desk lighting, music or data visualisation (an LED thermometer?), or art installations. They come in three different pixel-spacings.
Addressable LEDs, like these NeoPixel-compatible ones, let you individually set each LED in the chain to a specific RGB (or RGBW—red, green, blue, white—in this case) colour. You can use a Raspberry Pi, Arduino, micro:bit, or other microcontroller to code them, and there are tonnes of different Python, MicroPython (or CircuitPython), Arduino, and more code libraries available.
The extra warm white LED in these strips lets you set them to a nicer pure white colour, or to mix in white with the other RGB colours for lovely pastel hues.
These LED strips come in three different spacings—30 , 60, or 144 pixels per metre—and in metre lengths, so if you order a quantity of 1 then you'll get 1 metre, a quantity of 2 is 2 metres, and so on...
Be aware that if you order a 1 metre length of either the 30 or 60 pixel per metre strips then you may or may not get a connector on one or other of the ends. The 144 pixels per metre strips come ready-made in 1 metre lengths, so you'll get a connector on both ends of the strip with them.
The strips come with a flexible silicone waterproof sleeve, but this can be easily removed, if you like. If your metre length doesn't have a connector on one or other end, then you can use a little blob of hot glue to seal the flexible sleeve.