I found these in my bathroom and WC
These are silver fish (Lepisma saccharina) and harmless. Wikipedia says (image taken from the article):


  Silverfish are nocturnal insects typically 13–25 mm (0.5–1.0 in)
  long. Their abdomens taper at the end, giving them a fish-like
  appearance. The newly hatched are whitish, but develop a greyish
  hue and metallic shine as they get older. They have two long cerci
  and one terminal filament at the tips of their abdomens; the filament
  projects directly off of the end of their body, between the left and
  right cerci. They also have two small compound eyes, despite other
  members of Zygentoma being completely eyeless, such as the family
  Nicoletiidae.
  
  Like other species in Apterygota, silverfish are completely
  wingless. They have long antennae, and move in a wiggling motion
  that resembles the movement of a fish. This, coupled with their
  appearance and silvery scales, inspires their common name. Silverfish
  typically live for two to eight years. Silverfish are agile runners
  and can outrun most of their predators (including wandering spiders
  and centipedes). However, such running is possible only on horizontal
  surfaces, as they lack any additional appendages, and therefore are
  not fast enough to climb walls at the same speed.[citation needed]
  They also avoid light.