The genetic code is broken down into a series of codons on the mRNA. Each codon consists of 3 nucleotides which (normally) correspond to a single amino acid (e.g. AUG codes for methionine). I say normally because you can also have a codon indicate a stop codon (so no amino acid will be inserted and instead the polypeptide chain will terminate). This mRNA molecule with its list of codons will instruct a ribosome to synthesize a protein according to this code.
This code is the set of rules - based on the triplet or codon. This triplet code is universal - all organisms use the same codons to specify the placement of each of the 20 amino acids in a protein.
Because you will focus past ("overshoot") your specimen. (Like using a race car as a shopping cart: it's too fast, and you'll fly past the cereal and never even see it before you realize you need to stop.) Also: you risk crushing the slide and objective against each other (on older or cheaper scopes), and that would be a costly (and embarrassing) mistake.
Crystalloids are aquous solution of mineral salts or other water soluble molecules
colloids contains larger insoluble molecules such as blood and gelatin.
hope it helps u....