Personal pronouns after prepositions

What are the personal pronouns?

Yo, tú, él, ella, nosotros/as, vosotros/as, ellos/as (I, you, he, she, we, you, they)

What is a preposition?

de (of), a (to), con (with)...

In English, when we use personal pronouns after prepositions, the personal pronoun changes. For example "he" becomes "him":

"I am going to him" and not "I am going to he"

In Spanish, the personal pronouns after prepositions change as well, but only the first and second person singular change, the others remain the same:

mí (me)
ti (you)
él (him)
ella (her)
nosotros/as (us)
vosotros/as (you)
ellos/as (them)

Some examples:

Cuando se arrodilló ante mí no pude parar de reír. (When he knelt in front of me I couldn't stop laughing.)
Nadie estuvo hablando de ti. (No one was talking about you.)
Este libro es para ella (This book is for her.)
Este libro lo compré pensando en él. (I bought this book thinking of him..)

When we use the object pronouns "mi" and "tí" with "con" (with) we contract them with the "con" in the following way:

mi → conmigo
ti → contigo

Example:
Ella viene conmigo. (She comes with me.)