Oh dear, more info please! What kind of laurel spotted, or plain green (Aucuba or Prunus?) And 'inside' the leaves - what does that mean, inside the material of the leaf, or inside a stuck together, or curled up leaf? Are they just blackfly on the underside of the leaves?

Could be the nectaries that run either side of the mid rib (underside) of Prunus laurocerasus. I have noticed that they often develop sooty mould but are not a problem for the plant.

Need more info and a photo though to confirm exactly the plant and problem as Bamboo says..