Watching those amazing intra cell videos, it looks like the 'molecules' (those free-floating bits in the cell) that join other structures (by precisely finding the needle in the haystack) know where they are going? And how can they know by themselves? I wonder if they are 'escorted' by other 'molecules', and if so, don't those 'escort molecules' need to be escorted etc.? At some point, it seems there has to be an 'escort molecule' that knows where it's going without needing an escort, no? Is there a name to the 'molecules' that do this 'escorting'?