Question

if you observe a drop of blood under a microscope which cell would you see

Answer 1

red blood corpuscles, white blood corpuscles, plasma,

Answer 2

From a drop of blood on a microscope the following can be observed 
Plasma which consists of 80% proteins and 20% water and consists of the charge of blood like ions and cations. Its made of organic and mineral substances hence the charge 
Hematics 
This consists of platelets which stop bleeding, they aggregate the coagulation and stuff so you don't bleed to dealth. 
Leukocytes which consists of white blood cells which act as yo defence system and are in a variety such as neutropils and eosinopils and stuff. 
Erthrocytes!! This are red blood cells which carry oxygenated blood and deoxygenated blood, they look. Like coins or disc like on the middle. 

There is a lot on this study and if u want more if u need more check out books on Hematology.